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10 Surprising Facts About The Spread Of Disease

by Debra Kelly
fact checked by Jamie Frater

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.


Anti Smoking man
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.

fact checked by Jamie Frater
Debra Kelly

After having a number of odd jobs from shed-painter to grave-digger, Debra loves writing about the things no history class will teach. She spends much of her time distracted by her two cattle dogs.

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