10 ways parasites, bacteria, and viruses have been the scourge of humanity as long as we have been here, but disease has reshaped our history and influenced our evolution. Parasites helped give our immune systems the boost it needed to get up and running, and the humble bacterium has helped dictate the form this planet has taken. Sometimes, it seems that we humans are simply playthings in their hands, but they haven’t just been capricious forces that toss us around like rag dolls. These microorganisms have also done incredible things to help humanity.

10 The Viruses We Carried Out Of Africa Helped Us Survive

Thanks to the science of viral molecular genetics, we now know quite a bit about the bugs that infected us along our evolutionary path, and we have found that these hitchhikers have done quite a bit to help us along the way. For example, it was the evolutionary pressure they placed upon our immune system that made it as robust as it is today. Additionally, viruses may have played a role in the loss of specific receptors that we once possessed on the surface of our cells that infectious agents could latch onto and use to cause disease. By ridding the human body of this source of disease, viruses created a safer environment for themselves, benefiting everybody involved.

But they may have also played a role in ensuring that, among competing hominid species, it Homo sapiens that came out on top. While our species was developing, disease and parasites encouraged genetic diversity and weeded out the unfit. Once the first Homo sapiens left the continent, they brought their infectious agencies and parasites with them. If you’ve read about North American and European smallpox, you know how this goes.

While it wouldn’t have been the only factor, viral parasites would spread to other hominids like Homo neanderthalensis (Neanderthals), who wouldn’t have had any previous exposure to the new bugs and possessed a nasal structure that was less efficient at filtering air and keeping new viruses at bay. They would have devastated other hominid species, because the bugs were primed to live in similar environments, but the hominids were not primed to receive them. Models have shown that if Neanderthals had a mortality rate only 2 percent higher than humans, it would have been sufficient to cause their extinction after 1,000 years of competition. While disease was doubtless not the only factor, it would have certainly played a large role.

Most models of human disease evolution claim that they mainly evolved during the Neolithic era, after man moved out of Africa and populations increased, so there is some evidence of this selective viral pressure. Many of these early viruses have even been so successful that their genes have literally become a part of our DNA. For example, the human genome has been found to contain genes from the borna virus that were gained about 40 million years ago. In fact, scientists have isolated about 100,000 elements of human DNA that have come from viruses, mostly within what is called our “junk DNA.” The viruses that make up the majority of our junk DNA are called endogenous retroviruses, and they are so much a part of us that a scientist recently brought one “back to life” and even infected hamsters and cats with it.

9 Day Medical Uses Of Leeches And Maggots

For thousands of years, the European leech (Hirudo medicinalis) was used in medicine for bloodletting purposes, treating a wide range of disorders from hemorrhoids to ear infections. The practice goes so far back that an Egyptian painting from 1500 B.C. depicts their use. While some nations have never stopped using them, the practice fell out of favor in the Western world with the knowledge of bacteria and subsequent focus on the germ theory for medical treatment.

In the 1970s and 1980s, though, leeches made a comeback. Cosmetic and reconstructive surgeons found that they were an effective method for draining blood from swollen faces, black eyes, limbs, and digits. They are also helpful for reattaching small body parts like ears and flaps of skin, because they draw away blood that could clot and interrupt the healing process. Leeches have saved people from amputations and may even relieve the pain of osteoarthritis. Even veterinarians sometimes use them.

Maggots, on the other hand, are nature’s clean-up crew. They’re great for eating away dead or infected flesh, revealing the healthy tissue below in a process called debridement. They have also been found to be an effective treatment for ulcers, gangrene, skin cancer, and burns, among other things.

Maggots and leeches, as gross as they may be, are so effective that the FDA classified them as the first “live medical items” in 2010, paving the way for an entire industry called biotherapy. An organization called Biotherapeutics Education and Research Foundation (BTERF) has even sprung up to raise awareness of the new uses for these old critters, and there are several companies that sell them.

8 Evolved To Protect Us From Allergies

Researchers studying the effects of gastrointestinal parasites have come up with an astonishing theory: After parasites first colonized our gastrointestinal systems, they evolved over millions of years the ability to suppress our immune systems. At the same time, our own bodies evolved to partially compensate for the effect.

The astonishing part, and what this means for human health, is that once parasites and harmless microorganisms present in water and soil have been largely removed from their natural environment inside of us in developed nations through the use of modern medicine, our immune systems actually overcompensate for their loss, leading to allergies and even increased chances for asthma and eczema.

This “old friends” hypothesis (sometimes referred to as the “hygiene hypothesis,” though it’s actually more of a complementary theory) has gained more support in recent years as we identify new ways microorganisms have helped us survive over the eons. Clinical trials have been conducted using worms to test against multiple sclerosis, IBD, and allergies.

The main proponent of the old friends hypothesis is Graham A.W. Rook of University College London. He first proposed it in 2003, and since then, it has also been proposed as a possible cause of some forms of stress and depression.

Some people have taken the old friends hypothesis to its ultimate logical conclusion that if removing our parasites from society has led to health problems, we should put them back. In 2008, University of Wisconsin professor of neurology John Fleming conducted a clinical study in which he infected multiple sclerosis patients with parasitic worms to test their effectiveness against the disease. Over a period of three months, patients who had an average of 6.6 active lesions around the brain’s nerve cells were reduced to an average of two. When the trial was over, the number of lesions shot back up to 5.8 within two months. In earlier trials, the parasites appeared to have positive effects upon ulcerative colitis and Crohn’s disease as well.

Parasite therapy is still in the experimental phases, however, and probably has negative effects that outweigh the positive ones. As of now, the FDA has classified the worms as biological products that cannot be sold until proven safe. Only one species, Trichuris suis, has been approved for testing under Investigational New Drug (IND) status.

7 Virotherapy

One of the most exciting and promising branches of medicine in recent decades is virotherapy, a biotechnology technique to reprogram viruses to treat disease. In 2005, researchers at UCLA announced that they had turned one of humanity’s deadliest enemies into a cancer‑killer when they reprogrammed a modified strain of HIV to hunt down and destroy cancer cells. Around the same time, researchers at the Mayo Clinic in Rochester, Minnesota modified the measles virus to do the same.

The technique is similar to the one used to breed genetically engineered plants, in that a virus is used as a gene‑delivery vehicle. It has long been recognized as the most efficient means of gene transfer. This system is used for the production of useful proteins in gene therapy and has great potential for the treatment of immunological disorders such as hepatitis and HIV.

Viruses have been known to have the potential to treat cancer since the 1950s, but the advent of chemotherapy slowed its progress. Today, virotherapy is proving to be extremely effective against tumors without harming the healthy cells around it. Clinical trials of oncolytic virotheraphy have shown low toxicity and promising signs of efficacy. In 2013, a drug called talimogene laherparepvec (TVEC) became the first drug based on a tumor‑killing virus to succeed in late‑stage testing.

One of the biggest challenges facing researchers is how to deliver the virus where it will do the most good before the body recognizes it as an intruder and mounts a defense. Current research is looking into finding natural tumor‑targeting “carriers,” cells that can deliver the virus without either the cell or the virus losing its normal biological functions.

6 Using Viruses To Cure Bacterial Infections

Bacteriophages are viruses that specifically attack bacteria. First recognized by Frederick Twort in 1915 and Felix d’Herelle two years later, they have been used to study many aspects of viruses since the 1930s. They are especially common in soil, where many species of bacteria make their home.

Because phages disrupt the metabolism of bacteria and destroy them, it has been long recognized that they could play a role in treating a wide range of bacterial diseases. Because of the innovation of antibiotics, however, phage therapy was mostly shelved until the rise of antibiotic‑resistant bacteria generated a renewed interest in the field.

An individual phage species is generally only effective against a small range of bacteria or even one specific species (its primary host species), which was originally seen as a disadvantage. As we have learned more about the beneficial aspects of our natural flora, though, it has come to be recognized as the advantage that it is. Unlike antibiotics, which tend to kill bacteria indiscriminately, bacteriophages can attack the disease‑causing organisms without harming any other bacteria living inside us.

While bacteria can develop resistance to both antibiotics and phages, it only takes a few weeks rather than a few years to develop new strains of phages. Phages can also have an easier time penetrating the body and locating their target, and once the target bacterium is destroyed, they stop reproducing and soon die out.

5 Vaccines

Beginning in the 1790s, when Edward Jenner developed the world’s first vaccine against smallpox using a less virulent strain called cowpox to inoculate patients, vaccines have saved countless millions of lives. Since then, several different types of vaccines have been developed. Attenuated or “live” vaccines use live viruses that have been weakened or altered so that they do not cause illness, while inactivated or “killed” vaccines contain dead microorganisms or toxins that are usually used against bacterial infections. Some vaccines—including subunit and conjugate vaccines, as well as recombinant and genetically engineered vaccines—only use a segment of the infectious agent.

When a vaccine is injected, the pathogen goes to work, but there is not enough of it to replicate at the rate it needs to in order to take hold. The body mounts an immune response, killing the pathogen or breaking down the toxin responsible for disease. The body’s immune system now knows how to fight the disease and will “remember” if it comes across it again. In other words, scientists have figured out how to get a pathogen to help its own target defend itself against it. They have even taken the first steps toward developing vaccines for several forms of cancer, with three vaccines approved by the FDA for the hepatitis B virus (which causes liver cancer), human papillomavirus types 16 and 18 (which cause cervical cancers), and metastatic prostate cancer in some men.

Thanks to vaccines, several diseases have been driven to virtual extinction. Smallpox is the most famous example, but polio, though not totally eradicated, comes in at a close second. Several other diseases might be gone by now if vaccines weren’t so hard to come by in the underdeveloped nations that still struggle with them. Things are getting worse instead of better, with diseases coming in from an unexpected source: affluent, educated Westerners who should know better.

Unfortunately, the anti‑vaccination movement is making a comeback in regions where these diseases were once under control. Before the introduction of the measles vaccine in 1963, approximately 500,000 people per year were infected in the US, 500 of whom—mostly children—ended up dead. By 1983, there were only 1,497 cases reported, and after a brief resurgence in the ’80s and ’90s, reported cases were down to just 37 in 2004. After the anti‑vaccination movement began gaining traction, 118 cases were reported in the US alone in 2011. That number keeps growing, fed by travelers coming in from areas with higher rates and finding less resistance. Whooping cough, once thought to be gone forever in the US, is also on the rise.

4 Bacterial Waste Breakdown

Some of the smallest and simplest of creatures on Earth play some of the most important roles in safeguarding all of life. Bacteria have perhaps the most important role of all: breaking down and recycling waste.

The dead remains of animals and plants, along with the excrement of all organisms, contain vital nutrients and stored energy. Without a way to reclaim these nutrients, though, the available sources would be quickly depleted. Luckily, many bacterial species feed upon these energy sources, breaking them down to their smallest molecules and returning them to the soil, where they reenter the food chain.

As helpful as this process already is, humans have found many ways to exploit it for a variety of even more advantages. Bacteria are used in sewage treatment, industrial waste management, and the clean‑up of oil spills, leaked pharmaceuticals, and wastewater. They have also been useful in the development of aqua‑farming, algae control, and waterless toilets. Researchers and engineers are currently looking into their potential use in the production of environmentally friendly bioplastics, glues, and building materials. They may even be used to break down plastic waste.

3 We Would Quickly Die Without Our Gut Bacteria

Poorly understood until recently (and there is still quite a bit of research to be done), the natural bacteria that lives in our guts works with our immune system to drive out pathogens, produce vitamin K, stimulate peristalsis, and perhaps most importantly, digest our food. Without our gut bacteria, we wouldn’t be able to perform any of these functions, and we would quickly die.

The more we learn about beneficial strains of gut bacteria, the more we can incorporate that knowledge into healthy living. After it was determined that certain gut bacteria can play a role in obesity, probiotics became all the rage. Probiotics are the bacteria that reside in fermented foods and are now sold as supplements. Bacteria like some species of bifidobacteria, found in most yogurts, can create a highly acidic environment in which less‑beneficial microorganisms cannot survive. Fatty foods and stress can also play a role in the health of our stomach flora, killing beneficial bacteria while favoring the more harmful kind that cause gas, bloating, and “leaky gut syndrome.”

In a huge breakthrough in the study of our gut bacteria and what they do, a team of Chinese and Danish researchers have recently developed a new way to identify these microorganisms using DNA sequence data. They identified over 500 species of benign bacteria and 800 new species of viruses that could live off them, providing hope for new ways to treat diseases associated with them, such as diabetes, obesity, and asthma.

2 Skin Bacteria Serve As Our First Line Of Immune System Defense

The moment you emerged from your mother’s womb, you were set upon. They ambushed you in mere moments and colonized every inch of your skin, and they have been with you ever since. They are prokaryotes and other bacteria, and without the evolutionary partnership humans forged with them millions of years ago, you would have been dead soon after being born.

One of the most common skin bacteria is Staphylococcus epidermidis, a bug that we now know plays a role in fighting off Leishmania major, the cause of a nasty disease called leishmaniasis that results in skin boils and open sores that don’t heal. The good bug triggers an immune response called IL‑1 that the body can’t produce on its own, making Staphylococcus a necessary part of the human body, as vital to our existence as any organ.

Prokaryotes, which also colonize the digestive tract, cover every exterior surface on the skin. Along with the rest of our beneficial skin microbiota, they became a part of us when they started competing against less‑benevolent microorganisms for real estate. Along with the immune cells in our skin, they protect us against both pathogenic bacteria and opportunistic fungi that try to invade. This allows our bodies to spend less energy defending our exteriors and focus more on things like fighting viruses and precancerous cells.

While there is still much to learn before we can really use this knowledge in our health regimens, we are already looking to a future that involves the purposeful use of skin bacteria. A start‑up based in Massachusetts called AOBiome, for example, has created a body spray made of live cultured chemoautotrophic bacteria called Nitrosomonas. They claim that their spray can “replenish healthy skin bacteria” and even replace showering, as the bacteria live off the ammonia in our sweat.

1 Life As We Know It Wouldn’t Be Here Without Cyanobacteria

Cyanobacteria, or blue‑green algae, are possibly the oldest still‑living species on Earth, with fossils dating back 3.5 billion years. They are unicellular bacteria that grow in colonies, and if it weren’t for them, you wouldn’t be here, and neither would nearly every other form of life.

Cyanobacteria were the world’s first photosynthesizers. They used energy from the sun along with chemicals in primordial oceans and inert nitrogen in the atmosphere to make their food. As a waste product, they generated oxygen, a poison to virtually every other form of life at that time and the cause of early mass extinction events. Over a period of roughly 300 million years, all this oxygen generation helped form the atmosphere as we know it, during the Archaean and Proterozoic eras.

That wasn’t the only way this bacteria kick‑started life as we know it. Sometime during the Proterozoic or early Cambrian era, they formed a symbiotic relationship with certain eukaryote cells, making food for the cell in return for a stable environment to call home. These were the first plants, as well as the origin of eukaryotic mitochondria, which is essential for animal life. This truly titanic event is now known as endosymbiosis.

While several forms of cyanobacteria are toxic, a species named Spirulina was an important food source for the Aztecs and eaten regularly by many Asian nations. Today, it is often sold in powder or tablet form as a health food supplement.

You are not going to make it through life without getting sick. It happens to the best of us. What kind of sickness you end up with depends on a number of factors. Some illnesses are far easier to get over than others, while others feel like a death sentence the instant they’re diagnosed.

What 8217 s the Most Dangerous Microbe?

1 The Basics

Generally speaking, a virus tends to be more hazardous than a bacterium, though that’s a blanket statement that comes with a big “but.” The common cold virus is far less threatening than, say, botulism‑producing bacteria. Context matters.

Bacteria are single‑celled organisms that can survive on their own. Most are harmless, and many actually help us—our gut alone hosts roughly 100 trillion bacteria that aid digestion. Only a tiny fraction cause trouble. In size, bacteria are roughly ten to a hundred times larger than viruses, ranging from one to three microns, with Salmonella as a familiar example.

Viruses, on the other hand, can’t live independently. They act like parasites, hijacking a host’s cells to reproduce, which often results in illness or death. Their size is minuscule—about 20 to 200 nanometers across.

Parasites belong to the eukaryote kingdom, meaning they have a nucleus and internal structures, making them larger than both viruses and many bacteria. Some parasites are entire organisms, like tapeworms, that take up residence inside us.

Fungi most often appear as spores or molds. A common example is athlete’s foot, a fungal infection that thrives in damp environments.

2 Bacteria Breakdown

A solitary bacterium is a fully formed, single‑cell microbe capable of surviving outside the human body. They flourish in soil, rotting food, on skin—anywhere conditions are right.

The most dangerous bacteria can wreak havoc in several ways. Many produce deadly toxins that can paralyze or outright destroy our cells, disrupting normal function. Others multiply so aggressively that they outcompete healthy cells for resources.

Antibiotics have revolutionized medicine by either killing bacteria or halting their growth. They achieve this by either breaking down the bacterial cell wall or interfering with the organism’s ability to reproduce.

Because bacteria reproduce rapidly—every 20 to 30 minutes in ideal conditions—they also mutate quickly. This rapid evolution has given rise to antibiotic‑resistant strains. Some bacteria produce enzymes that deactivate antibiotics; others pump the drugs out before they can act.

Common culprits like Salmonella, gonorrhea, and Campylobacter have developed resistant strains, turning once‑easily‑treated infections into potentially lethal threats.

The ever‑changing nature of bacteria makes naming a single “worst” organism impossible. In 2024, the World Health Organization highlighted 15 drug‑resistant bacteria as especially dangerous. Near the top sits Mycobacterium tuberculosis, the bacterium behind TB, responsible for roughly 1.7 million deaths each year.

3 Virus Breakdown

Viruses aren’t cells or independent living entities. They consist of a tiny packet of genetic material wrapped in protein. Outside a host, a virus is inert—without a living cell to commandeer, it can’t replicate or cause disease.

Once a virus infiltrates a host, it hijacks the host’s cellular machinery to make copies of itself. This process often destroys the host’s cells, leading to infection. Their minute size even allows them to infect bacteria and fungi, and they can be inhaled, transmitted via insects, or spread through bodily fluids—pathways unavailable to larger microbes.

The immune system attempts to generate antibodies to neutralize the invader. If the virus replicates faster than the body can mount a defense, illness ensues and can be fatal. The viral replication cycle inherently damages host cells.

A fever is one of the body’s first defenses; many viruses can’t survive the elevated temperature, though prolonged fevers can be dangerous for the patient as well.

Antibodies are the second line of defense, but they require prior exposure to a pathogen to be produced. When encountering a novel virus, the immune system may be caught off‑guard.

Ebola is a stark example of extreme lethality, with mortality rates reaching up to 90 percent. Its rapid, deadly course, however, limits its spread compared with less‑virulent viruses.

HIV, by contrast, has spread worldwide and has claimed around 32 million lives. Modern antiretroviral therapies have dramatically reduced mortality, but the virus remains a historic heavyweight.

The 1918 influenza pandemic, often called the Spanish Flu, caused an estimated 50‑100 million deaths globally, underscoring how a seemingly ordinary virus can become catastrophic.

Rabies is another terrifying virus—once symptoms appear, the fatality rate is essentially 100 percent without prompt treatment.

Viruses that humanity has largely eradicated, such as smallpox, once killed roughly 300 million people before vaccination campaigns eliminated them.

4 Fungi Breakdown

Pop‑culture has turned fungal infections into something of a horror‑movie staple. Articles about bizarre fungi eventually inspired the video‑game series The Last of Us, where a cordyceps‑type fungus decimates humanity.

In reality, cordyceps infect insects, forcing them to climb and cling to vegetation before the fungus erupts from their bodies. Humans, with far more complex immune systems, are not susceptible to this particular pathogen—unless it somehow mutates.

Other fungi, however, pose real threats. In 2023, the CDC warned about Candida auris, a drug‑resistant yeast that spreads in hospitals and can invade the heart, lungs, bloodstream, eyes, bones, and other organs.

Cryptococcus neoformans, another ubiquitous yeast found in soil, can cause meningitis with mortality rates between 41 % and 61 %, especially in immunocompromised patients.

Aspergillus fumigatus, a common mold that thrives on decaying foliage, carries a mortality rate as high as 90 % in invasive infections. Everyone inhales dozens of spores daily, but most remain harmless—unless the immune system is weakened.

Fungal infections receive far less research funding than bacterial or viral diseases, yet they claim roughly 1.7 million lives each year—more than malaria and double the deaths from breast cancer. Over 150 million severe, non‑fatal fungal infections are reported worldwide.

5 Parasite Breakdown

Parasites are arguably the most unsettling microbes. While not always fatal, their size and life cycles make them especially creepy. They are living organisms that settle inside a host, often entering through disturbing routes.

Take Strongyloides, a nematode that thrives in contaminated soil. Walking barefoot can let its larvae burrow through the skin, travel via the bloodstream to the lungs, trigger a cough, and then be swallowed back into the gut, where they can reside for years, potentially turning lethal if the host’s immunity falters.

Giardia, a microscopic parasite, spreads through fecal‑contaminated water or food. Ingesting cysts leads to diarrheal illness, especially in areas with poor sanitation.

Tapeworms, contracted by eating undercooked meat harboring eggs, can stretch up to 12 feet inside the intestine, with some rare cases exceeding 50 feet and persisting for decades.

Brain‑eating amoebas, such as Naegleria fowleri, infiltrate the body through the nose when swimming in warm, stagnant water, leading to a near‑100 % fatality rate.

Parasites can also trigger sepsis and a host of other complications. Malaria, caused by Plasmodium parasites transmitted by mosquitoes, resulted in about 600 000 deaths in 2022 alone.

Most parasites don’t aim to kill their host; they need a living environment to survive. Roughly one in seven people worldwide harbors an intestinal parasite, and some estimates suggest up to half of humanity carries one at any given time.

6 So Which Is Worst?

It’s impossible to crown a single pathogen as the absolute worst. Each category—bacteria, parasites, fungi, viruses—contains a dizzying array of organisms with wildly different traits, transmission methods, and mortality rates. Variables such as geography, health status, and access to medical care dramatically shift the danger level.

The safest advice is simple: avoid infection whenever possible, regardless of the microbe. Prompt diagnosis and treatment are essential if you ever find yourself infected, whether the culprit is a bacterium, virus, fungus, or parasite.

Welcome to our deep‑dive into the top 10 mysterious viruses that continue to baffle researchers worldwide. These microscopic enigmas blur the line between life and non‑life, challenging our understanding of evolution, disease, and even our own genome.

10 Black Widow Virus

Scientists have recently uncovered a virus that harbors the gene responsible for the potent neurotoxin found in black‑widow spiders. This peculiar virus, known as the WO (Wolbachia‑associated) virus, zeroes in on Wolbachia bacteria living inside arthropods, using the toxin—latrotoxin—to puncture cell membranes and breach host defenses.

The presence of a spider‑derived toxin inside a bacteriophage is unprecedented; it suggests the virus has borrowed animal DNA to enhance its own infectivity. By creating microscopic holes, latrotoxin enables the virus to slip past immune barriers, marking the first documented case of animal genes inside a bacteria‑targeting virus.

Researchers speculate the virus may have snagged the genetic material after escaping a Wolbachia cell that had already invaded a black‑widow spider. Conversely, some argue the spider itself could have acquired the gene from the virus, flipping the usual direction of genetic exchange.

9 Infertility Virus

A shadowy viral infection is now suspected of accounting for roughly half of the puzzling cases of unexplained infertility. In about one in 70 women under the age of 44, doctors cannot pinpoint a cause, and a recent Italian study points to a member of the herpes family as the hidden culprit.

The investigation involved 30 fertile mothers and 30 women facing unexplained infertility. Thirteen of the infertile participants tested positive for HHV‑6A, a herpesvirus discovered three decades ago but still shrouded in mystery. None of the control group mothers carried the virus.

HHV‑6A appears to trigger an immune response that renders the uterine environment hostile to embryos. The virus also manipulates hormone pathways, releasing estradiol to prompt ovulation and prepare the womb, yet paradoxically sabotages implantation, leaving many women unable to conceive.

8 Survivor Virus

Scientists have recently unlocked the secrets of a virus capable of thriving in boiling acid. The SIRV2 virus infects the extremophile microbe Sulfolobus islandicus, which dwells in scorching, acidic hot springs where temperatures can exceed 80 °C (175 °F).

Using a Titan Krios electron microscope, researchers visualized how SIRV2 safeguards its genetic cargo by reshaping it into an “A‑formation,” a highly protective structural state. This adaptation grants the virus resistance to heat, desiccation, and intense ultraviolet radiation—traits reminiscent of bacterial spores that survive harsh environments.

Because the survival strategy mirrors that of resilient bacterial spores, scientists are exploring ways to harness SIRV2’s packaging system for advanced gene‑therapy vectors, potentially delivering therapeutic DNA safely through extreme physiological conditions.

7 Multicomponent Virus

Typical viruses pack all of their genetic instructions into a single particle that latches onto a host cell, injects its DNA, and hijacks the cell’s machinery. The Guaico Culex virus flips this script entirely.

To establish an infection, a host must encounter four distinct viral packages, each carrying a subset of the genome. A fifth optional component may also be required for full replication. This multipart strategy forces the cell to collect all pieces before the virus can replicate.

First identified in Trinidad’s Guaico region, the virus was uncovered during a U.S. Army medical survey of mosquito‑borne pathogens. While it appears unable to infect mammals, a closely related strain was later found in Uganda’s red colobus monkeys, hinting at a broader host range than initially thought.

6 Human Endogenous Retrovirus

Approximately eight percent of the human genome is a fossil record of ancient retroviral invasions. Retroviruses normally insert their RNA‑derived DNA into host cells, commandeering the host’s replication system to spread. When these invasions occur in sperm or egg cells, the viral DNA becomes a permanent fixture in every cell of the offspring, creating what scientists call endogenous retroviruses (ERVs).

Most ERVs have decayed into harmless remnants, but a small fraction remains functional. The HERV‑K family, for instance, still produces intact viral particles. Recent research uncovered a HERV‑K variant lacking the disabling mutations that typically render these sequences inert, suggesting it may retain the ability to replicate.

While the exact impact on human health remains uncertain, some researchers propose that HERV‑K may have conferred evolutionary advantages, perhaps influencing gene regulation or immune responses. The prospect of a dormant virus reawakening continues to intrigue virologists worldwide.

5 Bourbon Virus

A Kansas farmer succumbed to a baffling tick‑borne infection that began with nausea, weakness, and diarrhea before escalating to lung and kidney failure. Physicians initially administered antibiotics—standard care for most tick‑borne illnesses—but the patient’s condition deteriorated, leading to death after ten days in the hospital.

Only a single confirmed case of this disease, now termed Bourbon virus, has been documented, leaving clinicians uncertain about its full clinical spectrum. It could represent a highly lethal pathogen, or perhaps an atypical presentation of a usually mild infection. Preventive measures, such as wearing long trousers, applying repellents, and performing regular tick checks, remain the best defense.

4 Siberian Giant Virus

A French research team recently revived a 30,000‑year‑old giant virus—dubbed Sibericum—from deep Siberian permafrost. Extracted from soil 98 feet below the surface, the virus is massive enough to be seen with a standard light microscope and remains infectious after millennia.

The scientists used amoebae as bait, allowing the ancient virus to infect and kill these single‑celled organisms. Unlike most viruses that target the host nucleus, Sibericum establishes replication factories in the cytoplasm, a unique strategy among giant viruses.

Although Sibericum only infects amoebae, another giant virus, Marseillesvirus, recently caused illness in an 11‑year‑old French boy. These findings raise concerns that thawing permafrost could unleash dormant viral giants, especially as human activities like drilling and mining disturb ancient soils.

3 Deep‑Sea Virus

Explorations of the dark, nutrient‑starved ocean floor off California have revealed a surprising amount of biomass, much of it microbial. Within this hidden ecosystem, scientists isolated a virus that preys on methane‑oxidizing archaea—tiny, bacteria‑like organisms that consume methane at deep‑sea vents.

Researchers collected sediment cores from a methane seep, then supplied the samples with methane in the lab, prompting archaea growth and, consequently, the emergence of their viral parasites. The virus displays a fascinating arms race: it mutates a specific gene at its tail end—the region that contacts the host—while the archaea simultaneously evolve defenses, leading to a perpetual genetic tug‑of‑war.

Genetic analyses show partial matches between these Californian deep‑sea viruses and similar strains discovered near Norway, suggesting a surprisingly global distribution of these specialized viral hunters.

2 Mysterious Paralysis

In 2015, a wave of acute flaccid paralysis swept across American children, coinciding with an outbreak of the respiratory virus EV‑D68, a cousin of poliovirus. While EV‑D68 was detected in only about 20 % of cases, many researchers suspected another pathogen might be responsible.

One notable case from Virginia pointed to a lesser‑known virus, C105, previously identified only in Peru and the Republic of Congo. C105 is primarily linked to respiratory illness, but a handful of African cases displayed paralytic symptoms, making it a plausible suspect for the U.S. outbreak.

The mystery deepened because spinal‑fluid tests failed to reveal any enterovirus, the usual culprit for neurological damage. Although EV‑D68 remains a suspect, the absence of the virus in cerebrospinal fluid leaves room for C105—or perhaps an entirely unknown agent—to explain the paralysis.

1 Undiagnosed Hemorrhagic Fever Syndrome

South Sudan grapples not only with conflict and famine but also with a baffling viral outbreak that has claimed ten lives. Patients present with Ebola‑like symptoms—high fever, severe bleeding, and relentless vomiting—but laboratory tests have ruled out Ebola and other well‑known hemorrhagic fevers.

Blood analyses have uncovered a medley of viral signatures, including Onyong‑nyong, chikungunya, and dengue, yet none fully explain the mortality pattern. The disease appears to affect predominantly young people, with 75 % of victims under the age of 20, and there is currently no evidence of person‑to‑person transmission.

Scientists suspect a vector‑borne pathogen—perhaps transmitted by ticks or mosquitoes—but bacterial or parasitic origins cannot be dismissed. Ongoing civil unrest hampers comprehensive field studies, leaving the true identity of this “undiagnosed hemorrhagic fever syndrome” shrouded in uncertainty.

When you hear the word “virus,” your mind probably jumps straight to headlines about pandemics, feverish crowds, and global panic. Yet, the microscopic world of viruses is far more nuanced than that terrifying snapshot. In fact, among the countless viral species that roam our planet, there are several that quietly lend a hand to humanity. This list explores the surprising ways that 10 viruses actually help us, whether by battling bacterial foes, protecting crops, or even shaping the very fabric of our brains.

Viruses are everywhere—lurking in soil, swimming in oceans, hitching rides on insects, and even residing inside our own bodies. They can infect bacteria, fungi, plants, animals, and humans. While some viral outbreaks have caused historic devastation, researchers are uncovering a hidden side of virology: a roster of beneficial agents that could become essential tools for medicine, agriculture, and evolutionary biology.

Below, we dive into ten remarkable viruses that have proven to be more friend than foe. From the tiniest bacteriophages that could replace antibiotics, to ancient retroviral remnants that helped mammals give birth, each entry reveals a fascinating story of how these tiny entities support life on Earth.

Why 10 Viruses Actually Help Humanity

10 Bacteriophages

Bacteriophages—often simply called phages—are viruses that prey exclusively on bacteria. You can find them in nearly every environment, from garden soil to the deepest ocean trenches, and they even inhabit our own guts and mucous membranes.

Their discovery dates back to 1915 when Frederick Twort first observed their bacterial‑killing abilities. Since then, scientists have championed phages as a promising therapeutic weapon, especially as antibiotic resistance climbs to alarming levels.

Although phage therapy is still being refined, early trials have shown success against a range of conditions, from cystic fibrosis‑related infections to certain cancers. Some experts even envision phages eventually supplanting traditional antibiotics, offering a sleek, targeted strike against drug‑resistant bacteria.

9 There Is a Virus That Gives Plants Extreme Heat Resistance

Tropical panic grass thrives in soils that scorch well beyond the comfort zone of most crops. Scientists uncovered that a virus, living inside a fungal endophyte on this grass, bestows the plant with extraordinary heat tolerance.

Excitingly, researchers transferred this viral ally to other species, including tomatoes, and witnessed the same heat‑defying performance. The engineered tomatoes flourished in soil heated to a blistering 60 °C (140 °F) without wilting.

When the virus was stripped away, the plants lost their super‑heat resilience, underscoring the virus’s pivotal role—perhaps the botanical equivalent of the Human Torch’s powers.

8 Oncolytic Virus

Cancer evokes dread for anyone touched by the disease, and for over a century doctors have chased cures. Recently, an unlikely contender entered the arena: viruses that specifically target and destroy tumor cells, known as oncolytic viruses.

These engineered or naturally occurring viruses infiltrate cancer cells, replicate until the host cell bursts, and release tumor antigens that alert the immune system. In this way, oncolytic viruses act not only as direct killers but also as catalysts for a broader immune assault, positioning them as a novel form of immunotherapy.

7 Adenoviruses

Adenoviruses are a common family of viruses that usually cause mild, short‑lived illnesses such as colds, bronchitis, pneumonia, and even occasional cases of meningitis.

Beyond their reputation as everyday pathogens, a particular strain—type 52 (HAdV‑52)—has shown a knack for binding a unique carbohydrate present on the surface of many cancer cells.

This binding opens the door to virus‑based cancer therapies, where adenoviruses could be engineered to deliver therapeutic genes directly into malignant cells.

While research is still in its infancy, the prospect of harnessing adenoviruses to both target tumors and stimulate the body’s own defenses is an exciting frontier in oncology.

6 Norovirus

Noroviruses are infamous for sparking explosive outbreaks of gastroenteritis on cruise ships and in crowded settings, earning them the nickname “cruise‑ship stomach bug.”

Surprisingly, certain norovirus strains have proven valuable in laboratory mice raised in sterile environments. These mice typically suffer from weak T‑cell responses, compromising gut health.

Researchers discovered that introducing specific norovirus strains rebalanced the immune system, reducing weight loss and diarrhea caused by harmful pathogens. While giving noroviruses to humans remains controversial, the mouse studies hint at a therapeutic role for the virus in modulating immunity.

5 Ancient Retroviruses

Ancient retroviruses may be the reason we don’t lay eggs.

Scientists believe that endogenous retroviruses—viral DNA that became permanently integrated into the genomes of our ancestors—played a pivotal role in the evolution of the mammalian placenta.

In simple terms, a prehistoric virus likely infected an early mammal, inserting genetic material that later mutated to enable live birth. This viral contribution gave rise to the complex placenta, a critical organ for nurturing embryos inside the mother.

The placenta’s intimate relationship with the fetus mirrors a host‑parasite interaction, highlighting how a once‑harmful virus became a cornerstone of mammalian reproduction.

Ongoing research continues to unravel the extent of viral influence on our development, but it’s clear that ancient retroviruses helped shape the very way humans give birth.

4 Gamma‑herpesviruses

Gammaherpesvirinae is a subfamily of herpesviruses that includes several well‑known members, such as herpes simplex viruses causing cold sores and genital herpes.

Beyond the usual notoriety, latent infection with a specific gammaherpesvirus—mouse‑adapted MHV‑68—has been shown to bolster resistance against the bacterium Listeria monocytogenes, a common cause of food‑borne illness.

This unexpected cross‑protection suggests that certain herpesviruses may arm the immune system against bacterial invaders, turning a traditionally dreaded virus into an unlikely ally against food poisoning.

3 Cowpox

Smallpox, a devastating disease that plagued humanity for millennia, claimed roughly 30 % of those it infected and left survivors scarred for life.

In the late 18th century, English physician Edward Jenner observed that milkmaids rarely contracted smallpox, suspecting that exposure to a milder virus—cowpox—offered protection.

Jenner tested his hypothesis by inoculating a young boy with material from a cowpox lesion and then exposing him to smallpox. The boy remained healthy, confirming that cowpox could safely immunize against the deadlier disease.

This pioneering experiment birthed the practice of vaccination, ultimately leading to the global eradication of smallpox two centuries later.

2 GBV‑C

While HIV remains one of the most feared viruses of modern times, another virus—GBV‑C (also known as hepatitis G)—has drawn scientific interest for its surprising impact on HIV‑positive individuals.

People co‑infected with HIV and GBV‑C tend to experience a slower progression to AIDS and enjoy improved survival odds, a phenomenon that has fascinated researchers for years.

The exact mechanisms remain under investigation, but the protective effect of GBV‑C against a far more lethal virus highlights the intricate interplay between viral infections.

It’s a striking reminder that not all viruses are antagonistic; some may even act as quiet guardians against more dangerous pathogens.

1 The Arc Gene

Believe it or not, a virus may have been the catalyst for human consciousness itself.

Researchers propose that an ancient virus inserted its genetic material into the genome of a distant ancestor, leaving behind a fragment that persists in modern brains.

This fragment, known as the Arc gene, is crucial for learning and memory. Remarkably, the gene communicates between neurons by packaging and sending RNA packets—a process strikingly similar to how viruses move genetic material.

Ongoing studies aim to decipher exactly how this viral relic influences cognition, but early evidence suggests that our capacity for thought may owe a debt to a long‑lost viral passenger.

So the next time you marvel at a brilliant idea, remember: a tiny viral echo from deep evolutionary time might be whispering in your mind.

— Joshua Sigafus, writer and science enthusiast

Scientists are at it again. This time, they’re creating new viruses and bacteria in their laboratories. In this roundup of the 10 deadly viruses and bacteria engineered in labs, we explore how researchers tinker with pathogens, the controversies that follow, and why these creations matter for global health.

10 Deadly Viruses Overview

10 Horsepox

Scientists at the University of Alberta have created horsepox, a lethal virus closely related to the equally deadly smallpox. Unlike smallpox, horsepox does not affect humans and is only fatal to horses. The scientists created the virus during a six‑month study sponsored by pharmaceutical company Tonix. The researchers purchased DNA pieces via mail order and arranged them to form the virus. The entire project was not expensive. The DNA pieces used to create the virus cost just $100,000.

The study caused a dilemma at the time it was revealed. Other scientists were concerned that governments or even terrorists could use the knowledge to create smallpox virus for biological weapons. A smallpox epidemic could become deadly for us today. We no longer get vaccinated for it because we eradicated the disease in 1980.

The researchers clarified that they created the virus because they wanted to develop improved smallpox vaccines. Tonix later revealed that it had produced a smallpox vaccine with the horsepox virus. Other scientists say that the researchers could have extracted horsepox from wild horse populations instead of creating it from scratch. Tonix said they would have done just that if they had known they had natural access to the virus. However, lead researcher David Evans said they recreated the virus because Tonix would have been unable to commercialize the horsepox virus taken from the wild.

9 Black Death

Between 1347 and 1351, millions of Europeans were afflicted with a mysterious disease that killed over 50 million people. Today, we know this disease is the Black Death, which is caused by the Yersinia pestis bacteria. Although the Black Death is still around, it is not as potent as it used to be.

A few years ago, researchers from several schools, including the University of Tubingen in Germany and McMaster University in Canada, recreated the deadly bacteria from DNA samples extracted from the teeth of a victim who died during the plague. They got only 30 milligrams of the bacteria from the teeth, but that was enough to recreate it.

As a result, researchers confirmed the original bacteria’s relationship to the Black Death around today. Some scientists had claimed that the bacteria were of different strains, but they are now confirmed to be the same. The one we have around today only became less deadly after it mutated.

8 Polio

Like their counterparts at the University of Alberta, scientists at the State University of New York have created a deadly artificial virus by buying DNA pieces via mail order. This time, it is polio, and it is as potent as the natural one. Mice exposed to the artificial polio got sick just as they would have if exposed to natural polio.

The laboratory‑created polio was controversial among scientists. The researchers who produced it had taken its code from databases available to almost anybody. Other researchers fear that people with ulterior motives could develop their own artificial polio, which is much easier to make than other dangerous viruses like smallpox.

Smallpox’s genetic code is 185,000 letters long while polio’s is just 7,741 letters long. Although we are already at the brink of eradicating polio, scientists fear that we will still need to be vaccinated against the disease because it could be recreated.

7 Mousepox

A few years ago, researchers at the Australian National University and the Commonwealth Scientific and Industrial Research Organization (CSIRO) produced a deadly mutated strain of mousepox by mistake. Mousepox is another lethal virus that belongs to the same family as horsepox and smallpox.

The researchers were trying to develop birth control for mice at the time that they mistakenly created the virus. They inserted a gene that promoted the creation of interleukin 4 (IL‑4) into mousepox, which they injected into some mice. The mice were vaccinated and were not supposed to be harmed by the mousepox.

Instead of making the mice infertile as researchers had expected, the weakened virus turned lethal and destroyed the immune systems of the mice, killing them in nine days. The new mousepox was so dangerous that it was resistant to vaccination. Half of the other vaccinated mice exposed to the mutated mousepox also died.

The researchers were so scared by their invention that they did not want to publish their findings. They even met with the Australian military to confirm if it was safe to publish. Scientists fear that human smallpox could also mutate and become deadlier if injected with IL‑4. However, they are unsure because no one has tried it yet. We know it’s only a matter of time before some scientist does.

6 SARS 2.0

Severe acute respiratory syndrome (SARS) is a lethal virus. More than 700 people were killed during a SARS epidemic that infected 8,000 people in 29 countries between 2002 and 2003. Now, scientists have made it deadlier.

The new mutant SARS virus was created by a group of researchers led by Dr. Ralph Baric of the University of North Carolina. They call it SARS 2.0. The researchers developed the virus by adding some protein to the naturally occurring SARS. SARS 2.0 is immune to vaccines and treatments used to cure the naturally occurring SARS virus.

The team said that the research was necessary because the natural SARS virus could mutate and become immune to our vaccines. By creating a deadlier and mutated virus, we could develop stronger vaccines that will save us from a more lethal SARS epidemic. That is, if the natural SARS ever mutates.

However, other scientists are concerned because the SARS 2.0 that is supposed to save us from a deadly SARS epidemic could start that epidemic if it ever escapes from the lab.

5 MERS‑Rabies Virus Hybrid

Scientists have created a MERS‑rabies hybrid virus. The idea is to use the virus to develop a vaccine that will protect us from both viruses. Rabies is a deadly disease that can be transmitted to humans through the bites of infected dogs that usually have the virus in their saliva.

Middle East Respiratory Syndrome (MERS) is a new virus that appeared in Saudi Arabia a few years ago. It is closely related to SARS and is spread from bats to camels and, finally, to humans. MERS infected 1,800 people at the time of its first epidemic and killed over 630. Its fatality rate is around 35 percent.

As we mentioned in the previous entry, SARS infected over 8,000 people during a 2003 epidemic but killed just over 700. Although SARS caused more deaths in absolute terms, it has a lower fatality rate than MERS. Only about 10 percent of SARS victims died. And for now, we do not have any vaccine for MERS.

To create the MERS‑rabies hybrid, researchers took some proteins from the MERS virus and added it to rabies. They used the new virus to develop a new vaccine that made mice resistant to rabies and MERS. They believe that the vaccine can also be used for humans and camels at risk of getting MERS.

4 Phi‑X174

Phi‑X174 is another artificial virus we have produced in laboratories. It was created by researchers at the Institute of Biological Energy Alternatives in Rockville, Maryland. The researchers modeled the artificial virus after the natural phiX virus. PhiX is a bacteriophage, a category of viruses that infect and kill bacteria. However, it has no effect on humans.

The researchers created the artificial virus in 14 days, yet it resembles the natural virus so much that it is impossible to tell them apart. The researchers hope that the new virus is the first step in developing mutant and artificial bacteria that can be used for the benefit of man.

3 Unnamed Virus

Researchers from University College London and the National Physical Laboratory have created an unnamed virus that kills bacteria and behaves like a real virus. Like phi‑X174, it is a bacteriophage but deadlier.

The unnamed virus attacks any bacteria around it. Within seconds, it breaks into smaller parts that attach and create holes on the bodies of the bacteria. The holes quickly become larger, forcing the bacteria to leak their contents. The bacteria die soon after.

Despite its scary potency, the unnamed virus is not dangerous to humans and did not attack human cells during tests. However, it could enter human cells just like natural viruses. Researchers hope the results will be used for treat and study bacterial diseases in humans. The virus could also be used to alter the human gene.

2 Bird Flu

Some Dutch scientists have created a mutant and deadlier version of the already‑lethal bird flu. Natural bird flu is not easily transmitted among humans. However, the researchers altered it so that it could be. To test their new virus, the researchers exposed some ferrets to it. Ferrets were chosen because they had similar bird flu symptoms to humans.

Ten generations later, the already‑changed virus mutated again and became airborne. Natural bird flu is not an airborne disease. The study was controversial in the science community. It became even more so when the Dutch researchers attempted to publish the process to create the deadly virus.

Although scientists fear that terrorists could use the study to produce a deadly biological weapon that could kill half the people in the world, the researchers involved say that the study was necessary to allow us prepare for a mutated bird flu epidemic.

1 H1N1 Virus

In 1918, the world witnessed the arrival of a deadly flu epidemic. This was the H1N1 virus. By the time it was over, up to 100 million people were dead. The flu caused blood to seep into the lungs of victims. They released blood from their noses and mouths before drowning in the blood inside their lungs.

The flu returned in 2009. But it was less lethal even though it was mutated and deadlier than it should have been. Scientist Yoshihiro Kawaoka took samples of the mutated strain that caused the 2009 epidemic and used it to create a deadlier strain that was resistant to vaccines. This strain was similar to the one that caused the 1918 epidemic.

Kawaoka was not planning to produce a more lethal version of the flu at the time. He only wanted to create the original version of the flu so that he could study how it mutated and was able to bypass our immunity. The deadly virus is stored in a lab and could become fatal if ever released.

Welcome to the ultimate top 10 viral countdown that will make you look at the microscopic world in a whole new way. Viruses are the tiniest, most mysterious entities on the planet – they hover on the edge of what we call “alive” and can unleash planetary‑scale events with a single copy. Buckle up as we explore ten mind‑blowing facts that prove these microscopic ninjas are far more fascinating than you ever imagined.

Top 10 Viral Insights Explained

1 You Are Part Virus

Every human carries a hidden trove of viral remnants tucked inside our very DNA. Some viruses are clever enough to splice their genetic material into our genome, and if this happens in a sperm or egg cell, the viral DNA is handed down to the next generation. Over millions of years this has happened so often that roughly eight percent of a person’s entire genetic code consists of these fossilised viral sequences.

These viral fossils aren’t just dead weight – they can actually serve as molecular breadcrumbs that help scientists trace evolutionary pathways. When two different species share the same viral insert, it suggests a common ancestor that was infected before the lineages split. In this way, viruses become a timeline embedded within our own chromosomes.

Even though most of these viral fragments are inactivated, some have been repurposed by our cells. Certain human genes borrow viral promoters to kick‑start their activity, and a few viral‑derived proteins have been co‑opted into the immune system, turning ancient foes into allies in the ongoing battle against disease.

2 Viruses on Viruses

Meet Mamavirus, a giant virus discovered in a cooling‑tower water sample that loves to infect amoebae. The real surprise came when scientists found a much smaller virus hitching a ride on Mamavirus – a parasite of a parasite. They christened this diminutive invader Sputnik, classifying it as a satellite virus.

Sputnik can’t launch an infection on its own; it needs an amoeba already taken over by Mamavirus. Instead of commandeering the host cell directly, Sputnik hijacks the replication machinery that Mamavirus set up, using those viral proteins to copy itself. It’s a virus‑within‑a‑virus scenario that showcases just how layered viral ecosystems can become.

This discovery reminds us that even viruses aren’t immune to the relentless ingenuity of evolution – they can be prey, predator, and parasite all at once, weaving an intricate web of microscopic intrigue.

3 Giant (Reanimated) Viruses

While many of us picture viruses as tiny specks, some grow to sizes that rival the smallest bacteria. Researchers hunting for bacteria in a cooling tower stumbled upon a massive newcomer, later named Mimivirus because it mimics bacterial traits. Its genome stretches beyond 12 million base pairs, dwarfing the genetic material of many bacteria.

Further expeditions unearthed even larger specimens, including a colossal virus frozen in Siberian permafrost for over 30,000 years. When scientists thawed the sample and introduced it to amoebae, the ancient virus sprang back to life, infecting and replicating within its hosts despite its Stone‑Age origins.

The ability of such ancient giants to revive raises eyebrows about climate change: melting permafrost could potentially unleash long‑dormant pathogens, reminding us that the viral world still holds many secrets waiting to be uncovered.

4 Tiny Viruses

On the opposite end of the size spectrum, some viruses have stripped themselves down to the bare essentials. Take circoviruses that infect pigs – they pack a mere three genes into a genome of just 1,726 base pairs, a stark contrast to the human genome’s three‑plus billion base pairs. This minimalist design means the virus needs only a tiny protein shell, measuring roughly 17 nanometres across.

Researchers are pushing the limits even further, engineering artificial viruses that consist of just a handful of protein fragments and a sliver of DNA, measuring a staggering 12 nanometres in length. These synthetic particles could one day become tools for targeted drug delivery or gene therapy, showcasing how tiny viral scaffolds can be repurposed for human benefit.

The existence of both the tiniest and the gargantuan viruses underscores the remarkable flexibility of viral architecture – size truly is no barrier to success in the microscopic arena.

5 Mind‑Boggling Numbers

Counting every virus particle on Earth at any moment is a task that would make even the most diligent accountant break a sweat. Estimates place the total number somewhere between 10³⁰ and 10³², with many scientists settling on a round figure of 10³¹ – that’s a 1 followed by 31 zeroes. To put that into perspective, the observable universe contains only about 10²¹ stars.

If you were to line up every single virus end‑to‑end, using an average diameter of 125 nanometres, the resulting chain would stretch roughly 800 million light‑years. That distance would shoot far beyond our nearest galaxy and even outstrip the span of neighboring galaxy clusters.

These staggering figures illustrate not only how abundant viruses are, but also how invisible they remain to the naked eye. Their sheer numbers and minuscule size make them the ultimate hidden majority of life on our planet.

6 Nobel Prizes

If you’re dreaming of a Nobel Prize, a virus might just be your ticket. In 2020, researchers earned the Nobel in Medicine for uncovering the Hepatitis C virus, adding to a long line of laureates whose work on viruses has reshaped modern medicine.

The story begins in 1892 when Dmitri Ivanovsky showed that a filter could remove the agent causing disease in tobacco plants, hinting at an invisible culprit. This mysterious agent was later named “virus,” Latin for poison. Wendell Stanley later crystallized the tobacco‑mosaic virus, proving that viruses are particles, not liquids, and earned the 1946 Nobel for this breakthrough.

Since then, dozens of Nobel Prizes have celebrated viral research – from the development of the Yellow Fever vaccine to the discovery of how human papillomavirus triggers cervical cancer. These honors underscore the pivotal role viruses play in both disease and discovery.

7 Viral Antibiotics

Antibiotic resistance is one of the gravest threats to modern health, threatening to revert us to an era where a simple cut could be fatal. Enter viruses, specifically bacteriophages, as a potential new class of antibiotics.

Phages are viruses that prey on bacteria. After infecting a bacterial cell, they hijack its machinery, churn out thousands of viral copies, and eventually burst the cell open, releasing a fresh wave of phages to continue the assault. If scientists can pinpoint a phage that targets a deadly, drug‑resistant bacterium, they may have discovered a natural, self‑replicating antibiotic.

Research into phage therapy is heating up, but the concept isn’t brand‑new. In 1926, during a cholera outbreak in India, doctors collected stool from patients who had mysteriously recovered and administered it to the sick. Many recovered, likely because the stool contained phages that killed the cholera‑causing bacteria. Today, phage therapy is being revisited as a promising weapon against superbugs.

8 You Are Mostly Virus

Viruses are truly everywhere – wherever life thrives, viruses are close behind. While some make headlines with dramatic illnesses, the majority are so harmless we never notice them, yet they outnumber us by a staggering margin.

The human body houses roughly 10 quadrillion (10,000,000,000,000,000) human cells, a number that sounds massive but is dwarfed by the microbial world. Bacterial cells outnumber our own by about ten‑to‑one, and viruses dwarf even those, outnumbering human cells by roughly a hundred‑to‑one.

Most of these viral passengers target the bacteria that live on and inside us rather than our own cells. They silently shape our microbiome, influencing health in ways we’re only beginning to understand.

9 Viruses May Be The Origin Of Life

Evolution explains how life diversifies, but it doesn’t fully answer how life began. One compelling hypothesis flips the script, suggesting that viruses – the simplest self‑replicators – could have been the first spark of biology.

In the primordial soup, RNA molecules capable of self‑replication likely emerged first. These ribozymes could copy themselves and, through mutation, become more efficient. Because viruses rely on nucleic acids for replication, they fit neatly into this early‑life scenario.

The “Virus World” hypothesis posits that these RNA‑based entities pre‑dated cellular organisms, and the viruses that eventually learned to infect early cells are the ancestors of the viral diversity we see today.

10 Are Viruses Alive?

At first glance, deciding whether a virus is alive seems straightforward – you look, you see movement, metabolism, reproduction. Viruses blur that line. They’re built from proteins, lipids, and nucleic acids – the classic building blocks of life – and they can replicate and evolve, hallmarks of living things.

However, viruses can’t reproduce on their own. They must hijack a host cell’s machinery to make copies of themselves, leading most scientists to label them as non‑living chemical assemblies that excel at self‑propagation.

A minority of researchers argue that viruses should be considered alive because of their genetic complexity and rapid evolution. They compare a dormant virus to a bacterial spore: inactive yet poised to spring into life when conditions allow. Whether you view them as living organisms or sophisticated particles, the debate itself highlights the fascinating edge case that viruses represent in biology.

Viruses are a particularly fearsome “germ.” Though viral infections may resemble bacterial infections, antibiotics are useless against viruses. There are very few dedicated antivirals to kill them off. But who even knows if ‘kill’ is the right word to use for something that stretches the definition of ‘alive’? Viruses: they’re like microscopically tiny zombie-robots, hijacking cells and turning them into factories for themselves. But humanity can exploit viruses’ supremely odd workings and sneaky ways for their own purposes.

10. Blue Eggs

If you’ve ever wanted to find some green eggs for some Dr. Seuss-style green eggs and ham, you’re in luck. Thanks to a virus, you don’t even need the eggs of some exotic wild bird.

Most chicken eggs are white or brown, but a few chickens lay eggs that are green or blue. These breeds include the Chilean Mapuche breed, its descendant breed, the Araucana, and the Chinese Dongxiang and Lushi breeds.

Two things are responsible for the colorful eggs: viral infections and blood. Long ago, a Mapuche fowl was infected by a retrovirus, a virus which can insert its genetic code into the host’s. The retrovirus’s effect was to trigger the buildup of biliverdin in the eggshell, a breakdown product from a part of hemoglobin that can cause a greenish tint to bruises.

The Dongxiang and Lushi breeds developed their colorful eggs independently, but from the same viral cause. According to historical evidence, the Dongxiang breed has had the bluish-greenish egg mutation since at least 500 years ago, and the Mapuche fowl since between 200 and 500 years ago. The trait is autosomal dominant, so chickens need only one parent with the mutation to lay the colorful eggs. However, those who have both copies of the gene variant lay darker-colored eggs.

9. Tulip-breaking virus

For the beauty of a virus-infected egg, one only has to pay a little more than usual. But for a beautiful virus-infected tulip in the Netherlands of the 17th century, one had to pay a lot more.

Back then, some tulips mysteriously had beautiful streaking and feathering patterns. These are called “broken” tulips. They were so expensive, they could leave their owners “broke” too, as well as the whole Dutch economy.

In 1623, some bulbs were sold for 1,000 florins, when the average annual income was 150 florins. Due to their high price, it cost less for some citizens to get still-life paintings of “broken” tulips than the tulips themselves.

Their beauty was short-lived, as the broken tulips’ bulbs shrank over successive generations. Eventually, it could no longer flower, and soon died. No one knew what caused tulips to break. People turned to all sorts of odd things, such as pigeon dung, to try to reproduce the pattern.

It was later discovered a virus called a potyvirus made the tulips break. The infection spread through aphids or by contact with an infected tulip.The virus worked by affecting the distribution of the pigment anthocyanin.

Today, such tulips are still costly, but for the damage potyvirus poses to gardens rather than their beauty. Potyvirus-infected tulips, once so valuable, are now carefully weeded out of gardens. Now there are specially-bred tulips that mimic the patterns of a “broken” tulip, without the virus.

8. Electricity-Making Virus

Computer viruses were named after their biological counterparts. Now, biological viruses lead back to electronics.

Some solids build electric charges when compressed. This is called the piezoelectric effect, and it’s most well-known in quartz watches. The piezoelectric effect has several applications, but materials used to make piezoelectric devices are toxic and difficult to work with. This limits the widespread use of the piezoelectric effect.

Berkeley Lab scientists could change that with a virus. They used the M13 phage virus, which targets bacteria and is harmless to humans. It’s useful for several reasons: it multiplies itself by the millions, naturally arranges itself into orderly films like chopsticks in a box, and is easy to genetically engineer. The ease in genetically engineering it helps scientists boost its voltage, and its self-arrangement helps with the goal of self-assembly in nanotechnology.

The Berkeley Lab scientists tested their approach by making a generator. The generator works by tapping a finger on a stamp-sized electrode patch coated with viruses. The viruses then turn the force of the tap into electricity, producing enough current to operate a liquid-crystal display (LCD).

With this technology, future devices could be charged from the vibrations of everyday tasks, such as climbing stairs or shutting doors.

7. Battery Virus

Some computer and smartphone owners worry about viruses that can overclock their devices’ batteries and leave them with a useless metal brick. But biological viruses could do the opposite: make batteries better.

In 2006, scientists at the University of Massachusetts (MIT) used a virus called M13 to make part of a battery. This part, the anode, is part of a pair of poles in the battery with opposite electrical charges. In 2009, the scientists completed the tricker task of making the anode’s counterpart, the cathode.

To make it work, the scientists had to tweak two of the virus’s genes. The first gene made proteins in the virus’s coat. The modifications allowed bits of iron phosphate to stick to it and bulge “like tiny fists all along the length of the virus,” in the words of study co-author Angela M. Belcher. The second gene let carbon nanotubes attach, forming a network of millions of electricity-conducting viruses.

To make similar technologies, extremely high temperatures of about 660 degrees Fahrenheit (350 degrees Celsius) were needed. However, the researchers could turn M13 into a battery-making tool at or below room temperature.

According to Belcher, a third of an ounce (10 grams) of the virus battery could power an iPod for 40 hours. However, she believes it is more suitable for large, high-power things like electric cars.

In 2013, progress was made on that goal. With viruses, lithium-air batteries of electric cars could be greatly improved. The M13 virus was used to make manganese-oxide nanowires for lithium-air batteries. Unlike typically-made nanowires of the metal, the virus-made wires had a rough, spiky surface, which greatly increased the wires’ surface area. The increase in surface area could be a big advantage in the batteries’ charging rate. The process has other benefits, too, such as increased electrode stability and less need for expensive metals like palladium for the batteries.

6. Cancer-Fighting Viruses

Herpes and cancer: two diseases people really don’t want to talk about. But using herpes to fight cancer is definitely worth discussing.

Imlygic is a new anti-cancer drug. On average, it extends melanoma patients’ lives by less than four and a half months. This is barely statistically significant, but Imlygic is special: it’s made using a virus. To be specific, it is a live, infectious, modified version of HSV-1, the herpesvirus variety that’s the usual cause of cold sores.

Though Imlygic is not especially effective by itself, its flu-like side effects are mild compared to chemotherapy. When cells turn cancerous, their virus-fighting machinery breaks down. Herpesvirus prefers to attack cancer cells. When it attacks, the debris of burst-open cells alerts the immune system, and the immune system then targets the cancer cells.However, it is unclear whether the immune system targets all the cancer cells of the body, or only those infected by the virus.

Though Imylgic is the first to get approval in the US as a cancer treatment, it is not the only one in development. Tumor-killing viruses are a popular topic among scientists, and the idea has been around for decades. More virus-based cancer treatments may join Imlygic in the future.

5. Orange Virus Vaccine

It’s tradition to treat colds (which are caused by a virus) with orange juice. But, using viruses, the orange trees themselves can fight off bugs spread by bugs.

Citrus greening (or huanglongbing, to use the Chinese name) is a deadly disease for citrus trees. It is caused by the bacterium C. liberibacter, which is spread by sap-sucking insects.

Before citrus greening came around, the most devastating orange virus was the citrus tristeza virus. (or CTV) The virus was named after tristeza, a Portuguese word meaning “sadness”, for the sadness that came from the virus’s arrival.

Now these two major citrus pests will be pitted against each other, with the fate of the USA’s orange juice hanging in the balance.

Bill Dawson, a plant pathologist from the University of Florida, modified a local strain of CTV. With this, anyone could insert new bits of DNA into the virus’s genome and make it a protein factory. One of the world’s largest orange juice manufacturers, Southern Gardens Citrus, licensed the viral vector from Dawson’s lab. With the virus as a needle, all Southern Gardens needed was something to inject. The company chose genes from spinach, which coded for antibacterial proteins called defensins.

Southern Gardens plans on infecting trees with a harmless strain of CTV. Branches from CTV-infected trees would then be grafted onto other trees to spread the virus. As the virus copies itself, it becomes a spinach defensin factory, and the defensins destroy C. liberibacter.

Since the biology of the tree is not modified, orange juice from these plants would not have to carry a genetically-modified label. This makes getting regulatory approval much easier, sidestepping the issue of distrust of genetically-modified plants.

4. Food Poisoning Protection

It’s terrible to hunch over a toilet, waiting to throw up, and idly wonder which of the things you ate was germ-filled. Intralytix, founded in 1998, has a plan to give germs a taste of their own medicine, so to speak: it uses viruses to infect (and kill) bacteria that cause food poisoning.

Each of its products has a mix of viruses that target the same bacteria species.The company’s first product, ListShield, was approved in 2006. It is aimed at Listeria bacteria, which cause listeriosis, a kind of food poisoning with a death rate of about 20%.  ListShield is meant to be applied to ready-to-eat meats, such as deli meats and hot dogs. To kill off Listeria, ListShield is sprayed on meat and the drains, floors and other surfaces of a food processing plant.

Intralytix’s second product, EcoShield, is for the O157:H7 strain of E.coli. EcoShield is sprayed on meat before it is ground into hamburger to kill E. coli. In studies with government investigators, Sulakvelidze showed the product killed 95-100% of the E.coli strain within 5 minutes.

The two treatments are odorless, tasteless, invisible and non-corrosive. The concentration of phages in the liquid spray is 0.001%, making the product as harmless as water to anything but target bacteria.

Later, another company, Micreos BV, made its own phage treatments, Listex (P100) and Salmonelex. Listex (P100) targets a Listeria species, while Salmonelex targets Salmonella.

3. Antibiotic Viruses

Bacteriophages (or “phages”) are the natural enemy of bacteria. They copy themselves inside bacteria, and the bacteria eventually burst open with viruses.

In the 1920s and 1930s, doctors treated a variety of infections with phages. However, phage therapy had some problems. Scientists at the time did not know phages had to be matched precisely with bacteria targets to work, which made phage treatments unreliable. In addition, people sometimes became sick from the treatments because they were not purified properly.

After World War II, antibiotics were mass-produced. They were more reliable than phages, so interest in phages declined. Though phages were mostly forgotten in the United States, they weren’t forgotten in the Soviet Union. Due to the Iron Curtain blocking access to some of the best antibiotics of the West, the Soviets made do with phages and made phage therapy more effective. In the modern day, phage therapy administered in several forms, such as tablets, liquids, and injections, and remains a standard treatment in Poland, Georgia and Russia.

Unlike antibiotics, phages are very precise and leave the “good” bacteria of the body alone. With the rise of antibiotic resistance, phages might make a comeback in the English-speaking world.

2. Viruses killing other viruses

Ever heard the expression “fighting fire with fire”? Well, in this case it works, if by “fire” one means HIV.

In 2011, scientists at the University of California-San Diego and UCLA made a harmless version of HIV that relies on HIV to reproduce. This virus was called a therapeutic interfering particle, or TIP. By slowing the replication of the HIV virus, TIPs might give someone five to ten extra years before AIDS sets in.

The TIP’s genetic code was stripped to one-third of its original size, and it lacks important pieces needed to copy itself. The TIP can only copy itself by sneaking into HIV’s genetic code and copying when it does. TIPs also contain HIV-inhibiting sequences and compete for the same proteins as HIV. Leor Weinberger, the leader of the team that made TIPs, likens it to a “virus of a virus.”

According to Weinberger, TIPs could help with HIV “superspreaders.” These people, such as drug users, are responsible for a disproportionately large amount of HIV infection.

In 2016, scientists orchestrated another virus-on-virus match, this time between reovirus and hepatitis C. During childhood, reovirus can cause colds, but by adulthood most have been exposed to it and are immune. It’s like an early-game enemy: inconvenient at first, but a piece of cake once one’s gotten stronger.

In comparison, hepatitis C is like a final boss, one some find unbeatable. Hepatitis C is a common cause of liver cancer, and cancers originating from the liver is the third-highest cause of cancer deaths worldwide.

When this early-game enemy is pitted against the final boss…well, it’s the player (or rather the patient) who wins. When introduced to the body, reovirus stimulates a signal protein called an interferon, which activates a kind of white blood cell called a Natural Killer cell. In experiments on human cancer samples and mice, the Natural Killer cells then kill the tumor and cells infected with hepatitis C. The reovirus therapy could also be used for other cancers associated with virus infections, like Epstein-Barr virus-associated lymphoma.

1. Humans Made by Viruses

In The Matrix, bad guy Agent Smith likens humanity to a virus, a disease of the planet. In real life, he’s right… to a degree.

More than 45 million years ago, a mammal was infected by a retrovirus. By turning their RNA-based code to DNA, retroviruses such as HIV can sneak their instructions into the host’s genome. Whenever the host’s cell copies itself, it also copies the virus. This ancient retrovirus happened to infect a germ line cell and so could be spread to the primate ancestor’s offspring.

17 years ago, in 2000, a team of Boston scientists discovered a strange gene in humans. This gene, called syncytin, coded for a protein made only by cells in the placenta.

The two events are related: syncytin comes from the virus.

While the virus used that gene to fuse with a host cell, a developing fetus uses the gene to fuse some placental cells into one single-celled layer. This layer is essential for the fetus to draw nutrients from its mother.

The syncytin protein comes in two varieties, the previously mentioned being syncytin 1. Reflecting its viral heritage, syncytin 2 tamps down the mother’s immune system and prevents the immune system from attacking the developing fetus.

HERV-K inserted itself as recently as 200,00 years ago, making it the newest of all retrovirus genes in humans. It activates important genes that help with embryo development, and its viral particles and proteins help protect very young embryos from infection by other viruses.

It is estimated that over 8% of human DNA came from viruses.