For all our advances in medicine and science, disease outbreaks are still not uncommon. Many people suspect that a plague is one of the ways the world as we know it could end, and it’s a frightening thing to realize how scattered our knowledge of disease has been over the centuries.

10Xenophobia And Rudeness Combat Disease

Just because we know how germs work and how they spread doesn’t mean we’re not still coming up with new theories. Biologists from the University of New Mexico and the University of British Columbia suspect that we’ve come up with a rather ingenious way of preventing disease from spreading to our respective cultures over the years: We’re jerks.

In a nutshell, the theory states that we’ve developed cultures in which we view strangers and outsiders as people to be avoided and shunned rather than welcomed in order to make sure they keep their germs to themselves. The study examined a wide range of cultures and determined that those exhibiting lower instances of disease tended to be broken up into smaller, more independent groups with their own cultural identity and language rather than a unified culture.

The researchers have also argued that areas with lower rates of disease tend to be more standoffish and less affectionate toward strangers. These are places where gestures like hugging and kissing as a form of greeting are less acceptable. They also tend to form certain cultural taboos, especially concerning what’s acceptable to eat, that happen to keep people away from dangerous pathogens. The theory suggests that consciousness of disease has played a surprisingly large role in shaping cultures across the globe.

9The Five-Second Rule

We’ve all heard that if we drop some food on the ground and pick it up before five seconds have passed, it’s okay to eat it. Despite the shocking number of studies on the phenomenon, science can’t decide whether it’s true.

According to researchers from Clemson University, some bacteria like salmonella can live for up to a month on a typical kitchen floor and transfer instantly to dropped food. Another study by Aston University in the UK, however, tested E. coli and Staphylococcus transfer between food and different types of flooring and found that the longer food was in contact with the floor, the more bacteria was transferred.

It’s important to note that the two studies used different types of bacteria, suggesting that different bacteria act in different ways. It’s probably safer to just refrain from eating anything you drop.

8Sent By The Gods

In ancient Greece, not much was known about bacteria and the transfer of illness between people. They believed that disease was sent by the gods, going so far as to blame Zeus’s rage at the actions of a single person for plagues that swept through whole cities. Apollo and Artemis were often thought to inflict disease on the men and women who displeased them. Another story blames Pandora for releasing disease upon the world when she opened her box, although some texts—such as The Odyssey—suggest that both causes were true.

The spirits released by Pandora were called the Nosoi in Greece. In Rome, these personifications of disease and corruption were named Lues, Tabes, Macies, Morbus, and Pestis. The Nosoi were given characteristics like other gods: Morbus moved with a sort of world-weary exhaustion, Pestis was greedy, and they were all driven by Erinys, the personification of vengeance. According to Hesiod, when the Nosoi were created by Zeus, he took away their ability to speak so no man would hear them coming and no one would be able to escape them.

7The Work Of Robert Koch

Most of what we know today about bacteria was built on the foundation laid by Robert Koch. The German scientist who used newspapers to teach himself to read when he was five years old grew up to study at the University of Gottingen under a man named Jacob Henle, who was working on a theory that disease was caused by some sort of mysterious organism or parasite.

After serving in the Franco-Prussian War, Koch set up his own laboratory in his home. With the help of a microscope and some homemade lab equipment, he set about determining what this bacteria was that was supposedly had something to do with anthrax. He was eventually credited with confirming that bacteria was responsible for causing disease and could be transferred from one individual to another through the blood.

He also figured out that bacteria survive in unfavorable conditions by the creation of spores that can hibernate and spawn new bacteria once conditions are better. He experimented with different ways of raising bacteria so they could be more easily studied and outlined the conditions that must be present for bacteria to spread. Perhaps most importantly, he also wrote guidelines for the control of contagious disease, including the importance of keeping the water supply clean.

6Miasma

Throughout the Middle Ages, one of the major theories about how disease was spread concerned the presence of miasma, a toxic gas that built up in the soil when plant and animal matter decayed. From China to Europe, this was the scientifically accepted explanation for disease for centuries.

In the early 1800s, a French chemist named Boussingault performed a series of experiments to confirm the existence of miasma and its responsibility for making people sick. His search for the hypothesized hydrogen compound in miasma that was thought to be the cause was a failure, but discussions with a fellow scientist, Justus von Liebig, led them a step closer to the real culprit. Liebig theorized that something in the miasma, not the miasma itself, entered the bloodstream to make people contagiously ill.

The idea that miasma was somehow responsible for illness became more and more plausible with the growth of cities, especially during times like the summer of 1858, when the Great Stink caused by improper waste removal procedures hit Victorian London. The subsequent outbreak of cholera seemingly supported the miasma theory. Even Florence Nightingale believed in it, stating that one of the biggest sources of infection was drains in houses, which allowed the bad air to come back up into the home and infect entire families.

5Spontaneous Generation

Today, the idea that people believed in spontaneous generation as late as 1859 seems impossible, but there were tons of recipes for creating life from nothing, including the creation of mice from wheat husks and sweaty underwear placed in a jar, circulating well into the 19th century.

In 1745, a clergyman named John Needham boiled chicken broth until it was free of microbes before sealing it, reopening it later to show that more microbes had developed. This was supposedly proof that spontaneous generation was real.

Initially, the advent of germ theory only seemed to support the idea of spontaneous generation. It was thought that microbes were a byproduct of the disease rather than the cause of it, which fit right in with the idea that they were generated in the body from nothing. It wasn’t until Louis Pasteur published his work on the subject in 1859 that the theory was disproven.

4Lady Mary Wortley Montagu And Vaccinations

Lady Mary Wortley Montagu was a British noblewoman married to the Turkish ambassador. When the ambassador was sent to Turkey in 1716, he chose to take his wife with him. He didn’t know it at the time, but this simple act would be a major boon to Western knowledge of disease prevention.

Smallpox was an occasionally deadly and often disfiguring disease that ravaged England through the Elizabethan era. We now know that it was a plague as far back as ancient Egypt. While in Turkey, Lady Montagu saw several old women treating children by puncturing veins and exposing the blood to a small amount of smallpox toxin. As a result, they experienced a mild form of the illness before they quickly recovered, now equipped with a lifelong immunity to the disease.

Lady Montagu was astounded that they took the dose of the disease “as they take the waters in other countries” and returned to England with the knowledge. She even ordered the procedure to be performed on her own children. However, many remained skeptical, so Lady Montagu and the wife of the Prince of Wales decided to prove it was safe by convincing a group of prisoners at Newgate Prison to get inoculated. The death row prisoners were granted their lives for their participation in “The Royal Experiment.”

3Ayurveda And The Humors

One of the most common ideas in history about what makes a person vulnerable to disease is the concept that there’s something wrong with the body’s internal balance. In ancient Greece, the idea was that the body contained four humors, each governing a different part of it. The humors—black bile, yellow bile, blood, and phlegm—all needed to be in balance for health, and many methods of treating disease focused on bringing the body back into balance.

The theory was first formalized by Hippocrates and Galen as early as 200 B.C., but the concept is much older. In the ancient Indian system of Ayurveda, developed between 700 and 400 B.C., it is believed that an imbalance in the three doshas (pitta, vata, and kapha) is responsible for disease. The system used by Ayurvedic physicians to balance the three doshas is still popular today.

According to traditional Chinese medicine, which has been practiced for more than 2,000 years, disease can more easily spread to a body that is weakened by an imbalance of qi, or life forces. Many treatments, such as acupuncture, focus on returning this balance to the body.

2Super Spreaders Aren’t An Anomaly

Super spreaders are people who, for whatever reason, expose an extremely high number of people to an illness or a disease. One of the most well-known cases is Typhoid Mary, who spread typhoid to a large number of people without suffering from the disease herself.

When researchers study the spread of disease, they look at a variety of different factors to determine the cause, including how many people in a population are vulnerable to disease and how many people a single person exposes. For a long time, they had concluded that super spreaders are anomalies. That turned out to be a false assumption, however. In fact, there’s a good chance that there’s a super spreader in your house right now.

Children are among the most prolific super spreaders. It’s been found that vaccinating 20 percent of children is more effective at stopping the spread of illnesses like the flu than vaccinating 90 percent of people over the age of 65. Due to their immature immune systems, children are contagious longer than adults, and they are typically in contact with more people because of things like school and extracurricular activities.

1The Contagion Theory

The contagion theory of disease was first proposed by Greek physician and philosopher Galen, who had previously proposed the theory of the four humors. What we now know are germs are what Galen called the “seeds of disease.” These seeds, he guessed, were present in a person’s body and explained why some people developed a disease while others were unaffected.

This theory went overlooked in favor of the theory of the four humors, most likely because there was no way to prove or disprove who had these seeds in their system, while the humors were easily observed in all person. It gained new life, however, when a 16th-century physician named Girolamo Fracastoro began writing about the spread of disease. Not only did he believe that these seeds dictated who would fall ill, he also suggested that they could spread from person to person.

Fracastoro’s theories led to the containment of illness in Italy by quarantine, but for all the good he did, he also had a number of things wrong. He theorized that these seeds spontaneously develop within the body and certain seeds took root in certain humors. These disease-causing seeds would then need to be removed from the body by draining the corresponding humor. His theory soon fell out of favor because it couldn’t be proven, and after about 1650, he faded into obscurity.

Christmas is a time of kindness and charity. It’s the season of giving, and there are now more ways to give than ever. Whether you celebrate Christmas, another holiday, or no holiday at all, this cold, dark time of year is an excellent occasion to spread warmth far and wide.

This year, instead of exchanging presents out of necessity with a select few, try mixing your traditions up. Add a new habit to your celebration, and make it one that brings happiness to others. To help you get started, here are ten unusual and impactful Christmas traditions you can adopt to spread some joy.

Related: 10 Heartwarming Stories To Restore Your Faith In Humanity

10 One Simple Wish

Children in the foster care system, whether orphaned, victims of abuse, or in any other way disadvantaged, often struggle during the holidays. The absence of a stable home and family is often felt most strongly during this family-focused time of year. It’s hard to forget what you don’t have when it seems like the whole world is celebrating having it.

That’s where One Simple Wish comes in. The charity allows children in the foster care system to request specific toys and other Christmas gifts. It then lists them online along with some basic information about the child who requested it and the item’s price and asks anyone who is willing to pay for the item. The organization then buys the gift, delivers it to the foster child, and you gain the satisfaction of spreading joy to a place where it is sorely needed.

9 Pay it Forward

The Pay it Forward movement started as a series of small, anonymous charitable acts in the late ‘90s and has since grown into a major nonprofit charity organization. The idea behind Pay it Forward is simple: do something quick and easy for someone else and then encourage them to do the same. That process of chained charity creates a snowball effect that radiates goodwill from person to person.

A great way to join the movement is to donate to or join the official Pay it Forward organization at payitforwardfoundation.org or to simply get to work yourself. Something as simple as leaving five bucks behind at the coffee counter to pay for the person behind you can mushroom into a network of newfound joy.

8 Make Christmas Halloween

Yes, that sounds weird, but evolving demographics have begun to interweave old-fashioned Christmases with fresh, new traditions. Especially for the increasingly non-denominational youth, Christmas has become less about celebrating a man and instead about celebrating each other. For the younger generations, this had led to a lot more costumes, candy, cocktails, and creepiness.

Look at the recent resurgence in popularity for the demonic Krampus and Belschnickel or the slew of movies in the vein of Nightmare Before Christmas. Or tour the world for a whole host of witchy women that accompany Santa Claus on Christmas, such as the Mari Lwyd, the ogre Gryla, or Frau Perchta. Try one of the many Christmas-themed murder mystery games or the zombie-themed board game Dead of Winter. Not least of all, search Steam for Christmas horror games or Netflix for Christmas horror movies; you’ll be surprised how rich the genre already is.

7 Volunteer…on a Different Day

Probably the single most popular way to volunteer on Christmas is serving the less fortunate at a soup kitchen. The same is true for Thanksgiving—if ’tis the season to give, people tend to give at soup kitchens. It’s a kind, generous action, but there is one simple way to give back even more without doing any additional work: don’t volunteer on Christmas or Thanksgiving.

Don’t get us wrong: any time you volunteer to help the needy, you’re killing it at the game of life. But so many people volunteer on the holidays that some places don’t even have work for the volunteers. Instead, wait a few days, a week, or a month and volunteer then. Shelters need help all year round, so why not give to them when they need it most?

6 Help Those Stuck at Work

It’s an unfortunate reality that many people don’t have any Christmas traditions because they usually work that day. That is so often true for health and safety workers like police, firefighters, physicians, and service industry employees like waiters, cashiers, and cooks. One of the simplest and sweetest ways to spread joy during the holidays is to help someone who can’t celebrate themselves.

Bringing a festive or homemade dinner to those stuck in police stations or firehouses is a popular choice. It doubles as both a “happy holidays” and a “thank you for your service” surprise. Workers in the service and retail industries are in need, too, and a surprise, hot meal for someone stuck pumping gas or manning a pharmacy counter can go a long way toward making the season bright.

5 Donate Your Air Miles

Almost every major airline works in partnership with the Red Cross to allow frequent fliers to donate air miles to help volunteers get where they’re needed. Whether you fly United, Southwest, Delta, American Airlines, or any other big brand, donating your air miles to Red Cross workers is easy and impactful.

A simple Google search of the airline’s name and “donate” will take you where you need to go, and in turn, you get a Red Cross worker to where they need to go—helping those in need when they need it most. For many, accrued miles become an afterthought and sit unused, making donating them essentially a free option to give back.

4 Become an Elf

There are myriad holiday events in cities across the globe, and they offer one of the most fun and creative ways to spread joy: volunteering to dress up for kids. Whether as Santa Claus, Mrs. Claus, an elf, or any other character (there are a lot of Elsas these days), holidays parades and festivals rely on volunteers to dress up and make the magic real.

This Christmas cosplay may also be the most enjoyable volunteering experience out there. It can be a blast fielding questions from curious kids and improvising lore-friendly, family-friendly answers. And, if we’re being frank, young children could care less who the character is, so long as they’re big and bright, so volunteer as Spider-Man or Shrek if you’d like. It will spread joy, guaranteed.

3 Adopt a Soldier

The life of a soldier is a demanding one, and many are unable to secure leave for the holidays. Instead, they’re left to scrounge together whatever celebration they can while on their base. Luckily, you can help them out, and it’s actually pretty easy.

You can “adopt a service member” for the holidays by contacting your local military base and asking for their Morale Welfare and Recreation department. They can set you up to invite a service member to your house for Christmas. They’ll celebrate with your family and soak in some much-needed R&R in the comfort of a true home. Though they can’t be with their family, they can at least become a part of yours.

2 Fundraise Virtually

Technology has made fundraising easier and more available than ever. If you’re unable to physically volunteer or just can’t find the right place to donate your time and energy, or both, you can still reach people across the world. Virtual fundraising might be the answer. People are primed to give during the holidays, making Christmas fundraisers particularly productive.

One innovative way some have turned doing good digital is to host gala fundraisers over Zoom. The pay-for-a-plate event becomes a do-it-yourself dinner with the added bonus of safe socializing. There are infinite variations of virtual fundraising, most involving peer-to-peer networks and cleverly branded hashtags. They are exceedingly easy to start.

1 Celebrate Abroad

One of the absolute best ways to spread joy, not just during Christmas but throughout your life, is to experience and celebrate other cultures. Those who learn about their neighbors become closer to them and honoring each other breaks down invisible, alienating walls. Christmas is an excellent time of year to break down those boundaries, as its surplus of good cheer makes it easy to spread.

If you’re a small-town soul, try visiting New York City for Christmas and taking in the sights at Rockefeller Plaza. If you love artisan crafts (or just shopping), the Christmas Market in Nuremberg, Germany, is one of the largest in the world and still maintains a cozy, fairy-tale-esque feel. If you want to ditch the snow for the sun instead, try visiting the Honolulu City Lights festival in Hawaii, a month-long display of music, mirth, and—obviously—Christmas lights.