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. Some are pretty much death sentences the moment you’re diagnosed.

The cause of your illness can also vary greatly. Did you eat something that had gone bad? Chances are you picked up some kind of bacteria. Did you get sick after going swimming in some polluted water? You might have got a parasite. Did somebody sneeze on your bagel? You might have a virus. And let’s not forget that, if there’s mold growing in your house, you could be infected with a deadly kind of fungus. What a fun group!

In an ideal world, you’ll just avoid every kind of dangerous bacteria, parasite, fungi, and virus. But the world is rarely ideal. So what’s the most dangerous one of them all? If an evil wizard trapped you in a room with four doors, which would be the one that you’d be most likely to survive a walk-through? Let’s look!

The Basics

In general, a virus is more dangerous than a bacterium. Take that with a grain of salts, of course, because circumstances will vary. The virus that causes a cold is probably not going to be as dangerous to you as botulism.

Bacteria are single cells, and they’re able to survive on their own. Most bacteria are harmless, some are even helpful. Your gut has 100 trillion bacteria in it right now to help you digest your food. Only a small number of them are actually going to cause you any harm. Bacteria can be 10 to 100 times larger than viruses, or about one to three microns in length. Salmonella is a common bacterium.

On the other hand, viruses don’t do well on their own. They have a parasitic nature and require a host to help them survive. They need your body to reproduce and proliferate the cost of which is you getting sick and maybe dying. Viruses may be as small as 20 to 200 nanometers in diameter. 

Parasites, part of a group called eukaryotes (meaning their cells have a nucleus and internal structures) are larger than viruses and often bacteria as well. Some parasites can be whole, living organisms, like a tapeworm. 

Fungi are most often found in the form of spores and molds. Athlete’s foot is a kind of fungal infection.

Bacteria Breakdown

A single bacterium is a single cell. It is one complete little microorganism all on its own and can live outside of a human body. In fact, many bacteria happily reproduce in the soil, in rotten food, on your skin and anywhere else the conditions are right.

The dangerous kinds of bacteria can affect your body in a number of ways.  Many dangerous bacteria are able to produce toxins which can be deadly and are what lead to serious infections in the body. The toxins can paralyze the cells in your body or even destroy them, disrupting normal cell function and causing serious damage. Others can reproduce so prolifically that they crowd out your normal, healthy cells.

Thanks to antibiotics, medicine has been able to save countless lives by treating bacterial infections. Antibiotics can either kill or slow the growth of bacteria. They do this by either destroying the bacteria cell wall or limiting its ability to grow and reproduce.

Because bacteria are able to reproduce very quickly, some every 20 to 30 minutes, they’ve also been able to mutate quickly. This has given rise to antibiotic-resistant bacteria. Over time, the bacteria that has survived has mutated to develop various defense mechanisms against antibiotics. Some may produce enzymes that destroy antibiotics, and others have ways of removing the antibiotic before it can reach its target.

Some more common bacteria, like salmonella, gonorrhea, and campylobacter, have developed strains that are resistant to antibiotics. This means that any infection that may have been considered easily treatable could become far more dangerous and deadly as it evolves. 

Because of the ever-changing nature of bacteria, it’s hard to choose the “worst” of them all. In 2024, the World Health Organization issued a list of dangerous, drug-resistant bacteria and there were 15 chosen. Near the top of the list were bacteria that cause tuberculosis, called mycobacterium tuberculosis. This is potentially the deadliest bacterium in the world and is responsible for 1.7 million deaths per year. 

Virus Breakdown

Viruses are not cells or living organisms on their own. Instead, a virus is a small amount of genetic material that is encased in protein. A virus can only work if it’s inside a living organism. On its own, it’s nothing, it has no function or purpose. 

Once inside a host organism, the virus uses the cells of that living organism to replicate. This process can end up destroying cells and leading to infections. Because viruses are so small, they can even infect bacteria and fungi. You can breathe them in or contract them through things like mosquitoes in ways that bacterial, parasitic, and fungal infections can’t because they are larger.

While a host body will try to produce antibodies to fight off a virus, if they get overwhelmed, and the virus can replicate faster than the host organism can fight it off, that’s when sickness takes over and the potential outcome is death. The viruses need your cells to reproduce because they don’t have the material or energy to do it on their own. This process destroys your cells.

Your body will fight back by raising the temperature. That’s what a fever is. Viruses tend to need a very delicate balance of temperature to survive and even a few degrees too warm can kill them. Unfortunately, a prolonged fever is dangerous for you as well. 

In addition, your immune system will try to use antibodies to fight the virus if it can. It needs to be exposed to a pathogen before it can make antibodies, however. If the virus is something you have never experienced, you will have no antibodies at first and your immune system may not be able to fight back. 

A virus like Ebola is extremely deadly. Up to 90% of people who contract Ebola will die from it. While that’s terrifying, it also ends up being one of Ebola’s weaknesses. Because it kills so quickly, the disease is not able to spread as well as others that don’t have such a high, swift mortality rate. Outbreaks, once isolated, tend to burn themselves out before they spread too far from the source. 

Judging the danger of a particular virus can be tricky. While Ebola kills up to 90% of people who contract it, it’s not widespread. However, HIV has spread all over the globe and is arguably one of the deadliest diseases in history. As many as 32 million people have died from HIV. That said, new treatments have greatly reduced the overall mortality rate, and the odds of dying from HIV now, with treatment, are very low.

In 1918, a flu pandemic killed somewhere between 50 million and 100 million people. 

Rabies is another virus that can seem quite common but is exceedingly dangerous. Without proper treatment, the mortality rate for humans infected with rabies is nearly 100%.

Viruses we have mostly eradicated were far deadlier than what most modern people can understand. Smallpox, for instance, killed about 300 million people. 

Fungi Breakdown

Thanks to pop culture, most people are familiar with just how terrifying a fungal infection can be. What first gained attention as quirky articles on the internet were then made into a worldwide phenomenon in the game and subsequent TV show called The Last of Us.

In The Last Of Us, much of mankind has been wiped out by a fungal cordyceps infection. Cordyceps is a real thing that has been seen infecting far less complex organisms like ants. The fungus grows inside of them, literally breaks through their bodies, and forces them to keep moving like zombies even when they should be dead. Fascinating stuff, but not applicable to humans. Our immune systems are vastly more complex than an insect’s and, as a result, we are immune. Unless it mutates one day. 

While cordyceps won’t kill you anytime soon, it doesn’t mean other fungi aren’t a danger. In 2023, the CDC warned about the rapid spread of Candida Auris. The fungus is resistant to most antifungal medications and was putting people in the hospital on ventilators. The infection can spread into your heart, lungs, blood, eyes, bones and organs.

Another fungus, cryptococcus neoformans, has a mortality rate between 41% and 61% and is especially dangerous to those with an already compromised immune system. The fungus, a kind of yeast, is found all over the world in soil. It can cause a kind of meningitis.

Aspergillus fumigatus is a kind of mold and has a mortality rate as high as 90%. You can find it almost anywhere that leaves fall on the ground and start to rot. Estimates suggest all of us inhale between 10 and 100 Aspergillus spores every day. 

The problem with Aspergillus and other fungal infections is they receive less attention and fewer resources than bacteria and viruses. Also, fungi are quick to adapt to medications and become resistant. Nevertheless, as many as 1.7 million people per year die from fungal infections, which is more than malaria and twice the number who die of breast cancer. There are over 150 million severe infections reported that are damaging but not fatal, as well.

Parasite Breakdown

Parasites are, hands down, the creepiest and most disturbing things that can infect you. Even if they aren’t as deadly as other infections, they tend to be more off-putting if for no other reason than many of them are big. These are living organisms that take up residence inside of you. The way they get inside of you can be just as disturbing as the fact they are inside you.

Take Strongyloides, for instance. This parasite transmits through feces but can live in soil for weeks. If you walk barefoot across it, they will burrow through the flesh of your foot. They’ll ride your bloodstream all the way to your lungs and then cause you to cough. Coughing brings them to your mouth where they get swallowed into your gut, right where they want to be. They can live for years in there and may turn deadly depending on the medications you take.

Giardia, a small parasite, is transmitted most often through feces or things contaminated with it. You can get it on your hands or in the food you eat and ingest it without realizing, as it’s a small, one-celled organism. 

Tapeworms, which can infect you if you accidentally ingest their eggs in undercooked meats, or from meat handled unhygienically, can grow to be up to 12 feet long in your gut, but some have been reported to be over 50 feet. They can live for 30 years.

Brain-eating amoebas have been contracted by people swimming in still, warm bodies of water like ponds in the US. They enter through the nose and infect the nervous system with a near 100% mortality rate. 

Parasitic infections can lead to sepsis among numerous other symptoms. One of the most well known and deadly parasites is the malaria parasite, transmitted by mosquitoes, which caused over 600,000 deaths in 2022. 

As disgusting as parasites can be, many of them will not actually kill you. It’s not in a parasite’s interest to kill its host, after all. It’s estimated about one in seven people in the world currently have an intestinal parasite. Some estimates boost that to about half the world’s population. 

So Which is Worst?

You can’t make a strong claim that any one of these deadly pathogens is better than another. There is far too much variety among each category to conclude one is preferable to another. In addition, there are so many mitigating factors that can alter just how dangerous an infection from one of these pathogens could be.

It’s much easier to state that you really don’t want to get an infection of any kind, be it parasitic, fungal, viral or bacterial. None of these are going to be a good time for you, and all should be avoided or treated quickly if they ever come up.

Mushrooms and fungi are very familiar to most of us, love them or hate them, they’re known to most for their culinary or medicinal uses, or perhaps as annoying mould or the yeast we use to bake. It’s a safe bet to assume that nearly anyone’s heard of them, seen them, used them, tasted them, however, these ones are vastly different, steering further into the realms of fantasy—horrifying, interesting, or just plain weird.

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10 Lobster Mushroom

Despite what its name would suggest, the lobster mushroom is actually not a mushroom, at least, not entirely one.

Hypomyces lactifluorum is actually a species of mould, a bright orange, parasitic fungus that spreads over its naturally white host and transforms its appearance into something which is a lot more vivid—like a lobster!

They prioritise Russula or Lactarius mushrooms and they’re, in fact, known to produce an allegedly extremely delicious combination! The name “lobster mushroom” certainly sounds appetising, though you’d be forgiven if you weren’t that enticed by the mould part, but generally speaking, a parasitically transformed orange mushroom which smells like shellfish, and in Lactarius’ case, transformed from a hot, peppery mushroom into something mild and delicious, is possibly one of the coolest things one could eat.

Some level of care is advised though; while mushrooms of the Russula or Lactarius genus are perfectly edible, it is technically possible for Hypomyces lactifluorum to target a poisonous mushroom, accidents like that are virtually unheard of but being careful is still important—never eat something you picked if it hasn’t been identified by a professional.

9 Giant Puffball

Readers from certain places of the world may be a little surprised to see the giant puffball mushroom on this list as, for how strange it actually is, it’s actually surprisingly common throughout mainland Europe, even rarely appearing in the UK!

Giant puffball mushrooms, like their name suggests, are quite massive, smooth, and a pure white in appearance, certainly befitting the title of a ‘puffball’.

These mushrooms may grow to be over a metre in diameter and may “explode” in order to spread their powdery spores contained inside.

Despite their strange description, they’re also edible and fairly popular to forage, also considered pretty safe, perhaps unsurprisingly, as not many other mushrooms could be confused with a large, white, spherical, vaguely alien-looking thing.

One thing to note though, if you suddenly have a craving for these otherworldly-seeming mushrooms, aside from taking our advice from the #10 entry, make sure the inside is a pure white, by the time it’s yellow or brown the spores have begun to ripen and the mushroom becomes inedible.

8 Mycena Chlorophos

Next on our list of fantasy mushrooms is something which is perhaps more conventional looking at first but extremely interesting and, actually, beautiful!

Mycena chlorophos is a mushroom which is naturally luminescent! This small mushroom grows in groups and it emits a clear green glow in the dark, making for a wonderful sight if you happen to spot one, which, sadly, isn’t all that likely.

As wonderful as this species is, they’re still fairly mysterious and unknown, in large part due to their limited range, being constrained to certain areas of mainly subtropical Asia, though also found in tiny portions of Brazil and Australia where it was likely transported and introduced artificially.

Due to how rare and unknown it is, its edibility is unknown, however, it’s best to not get your hopes up as the mushroom is said to smell of ammonia.

They’re typically found within woody debris, and while not glowing indefinitely, it displays its beauty for about 72 hours after developing, certainly a sight to see by all means!

7 Indigo Milk Cap

Lactarius indigo, also called the indigo milk cap, indigo lactarius, or the blue milk mushroom is a beautiful mushroom with a striking blue colour, its cap measuring up to 15 cm-s or roughly 6 inches wide, it’s frequently praised and treasured for its unique beauty and odd features, it’s sought out by edible mushroom enthusiasts as an enticing-looking oddity.

Its common name isn’t there just for show either, quite aptly, when you cut the flesh or damage the gills, this mushroom exudes a colourful, blue, milky, latex-like liquid, vastly different from the white ‘milk’ of its closest relatives.

The indigo milk cap is also mycorrhizal, just like chanterelle mushrooms, it grows close to trees and, in a mutually beneficial relationship, they exchange certain minerals and nutrients with each other!

The mushroom is also edible, though it’s generally best described as plain-tasting or even bitter, not extremely delicious or something to really seek out unless you really want to tell the story of eating a blue milky fungus.

6 Bearded Tooth Mushroom

Hericium erinaceus, also known as the lion’s mane mushroom or the bearded tooth mushroom is a medicinal and edible forest mushroom found in North America, Europe, and Asia with looks that could really rival the designs of many fictional plants!

They grow on trees and appear as large and incredibly cool looking lumps on them, appearing as a cascade of spines that are sometimes likened to icicles due to their long, sharp, downwards-growing shape and typically white colouration, though eventually yellow or brown with age. As its name would suggest, it could be described as looking like a beard or an animal’s mane!

Aside from being edible and described by some as a special treat, being widely consumed in China and Japan, it also has plenty of medicinal usages dating far back in history as a part of traditional Chinese medicine. Modern research has shown that it contains compounds that are effective against memory loss, anxiety, depression, dementia, neurological disorders, and even cancer!

If a beard- or mane-looking, large, spiny mushroom that grows on trees and is both flavourful and medicinal doesn’t sound like it’s from a fantasy story then I’m not sure what does.

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5 Shaggy Ink Cap

It’s certain that we’ve covered a lot of intriguing and strange mushrooms and fungi already but this one is quite special!

Coprinus comatus, or, by other names, the shaggy ink cap, shaggy mane, or the ‘lawyer’s wig’ mushroom, aside from having incredible names, is quite incredible by itself as well! It’s a reasonably common, small, egg-shaped mushroom which is naturally white and is frequently found in woods, meadows, fields, and even suddenly appearing in troops on people’s lawns!

These interesting and varied looking fungi, aside from having the habit of suddenly appearing in places and growing in troops, lines, or other various formations are also known for their colouration, starting off white, the gills deliquesce, meaning, they slowly decompose and liquidify into black ink, creating a beautiful gradient and slowly turning black, which also happens to be the colour of its spores.

It may be quite sudden to appear and it’s not the rarest mushroom out there but it’s certainly an incredibly interesting sight to see!

4 Black Brain Fungus

Exidia glandulosa comes in with perhaps the best common name on our list yet, the black brain fungus (also known as black witches’ butter fungus) certainly matches that description with an amazing black colouration in wet weather and greasy, butter-like looks, almost a tar-like appearance.

This fungus appears throughout Europe and North America throughout the winter and autumn and it’s often received divisively, having looks some may describe as beautiful and intriguing or others as downright gross, but in either case, it’s hard to deny how unique it truly is!

It’s frequently found on dead wood and fallen branches and it’s described as, expectedly, squishy or gelatinous in texture. Its edibility is sadly classified as dubious at best and even if it was safe to eat, it likely has no substantial nutritional value to speak of, so, as incredible as it looks, it’s probably best to just opt to go for real butter if you’re hungry.

3 The Devil’s Cigar

Chorioactis, known as the devil’s cigar or Texas star in the United States or kirinomitake in Japan, is a pretty and extremely rare genus of fungi which only contains one species; Chorioactis geaster, the literal, nearly aptly-shaped star of this part of the list!

This pretty and almost star- or flower-shaped mushroom is known for its looks and extremely strange distribution, sometimes cited as one of the rarest mushrooms in the world, it’s actually only found in a few Texas counties and a small number of locations in Japan, its placement almost seeming near random!

Rarity and appearances aren’t the only reason it’s on this list however, this mushroom, interestingly, looks like an American football or a cigar in the early stages of its life before it splits apart, releasing its uniquely massive, also cigar-shaped spores with an audible hiss and sprouting into an enticing flower-like fungus with three to six rays or ‘petals’.

2 Chicken of the Woods

Laetiporus sulphureus, the chicken of the woods, is a large, yellow- or orange-coloured edible polypore mushroom which grows on trees, and, just like the other things on this list, comes with some certainly interesting quirks aside from its unique appearance.

Most notably, the chicken of the woods.. tastes like chicken! Yes, really!

It’s quite common to proclaim that something tastes like chicken, often as a subject of a joke, however, in this case it’s really true! This mushroom is fairly high in protein and, as such, it’s a fairly popular vegetarian alternative to chicken!

Frequently consumed fried in breadcrumbs, it’s said to be best when it’s picked young and moist and keeps well frozen too.

A notable downside to this meat-free chicken, though, is that a small percentage of people experience nausea or side effects after eating it and it’s important to make sure that it hasn’t been imbued with potentially toxic substances from the tree it was growing on.

As long as those factors are considered though, this may just be an incredibly interesting and potentially incredibly tasty mushroom to look for!

1 Bleeding Tooth Fungus

We’ve arrived at the final fungus on our list and, fittingly so, it has the most unbelievable and incredible looks of any on this list, Hydnellum peckii or the bleeding tooth fungus, devil’s tooth, or even ‘strawberries and cream’, is another aptly described one.

The adult form is, admittedly, not that special, however, when the fungus is young it’s an entirely different story!

The off-white, almost beige or pink colouration is dotted with many, many ‘pores’ which oozes a striking, vivid, red or dark red liquid which is extremely reminiscent of blood.

This liquid, actually a type of sap, makes it look like the fungus is bleeding from multiple holes thanks to a red pigment found within the organism.

This fungus isn’t all scary though, a chemical found in it, thelephoric acid, is seeing experimentation as a potential treatment for Alzheimer’s disease!

And, finally, if you were hoping to get a taste of this incredible species, while it’s not toxic, it is, however, said to be extremely bitter and thus sadly classified as inedible.

At the end of the day, it may not be tasty, but it would surely make an eye-catching cover for a fantasy novel!

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About The Author: Just a British person with an extreme interest for all things weird and intriguing!