The cholera bacteria was first isolated in 1854—but the discovery was largely ignored

Robert Koch won the Nobel for his tuberculosis work, but he also pioneered cholera research

Koch was one of the first scientists to isolate the bacterium that causes cholera while investigating an outbreak in Egypt in 1883. He went on to advise about rules to control cholera outbreaks, which formed the basis of the disease control approaches and water hygiene techniques still used today.

In 1892, two scientists purposefully infected themselves with cholera bacteria

When they became ill—one with mild diarrhea and the other with severe cholera—researchers pointed to that as proof that the pathogen caused the disease.

Cholera went global thanks to global trade

The first cholera pandemic grew from an outbreak in India, in 1817. Scientists suggest it spread from there throughout the continent and onward to Africa, Russia and Europe through the poop of traders.

John Snow—not the one from 'Game of Thrones'—determined that contaminated water sickened London

His pioneering epidemiology work during an 1854 cholera outbreak mapped out the commonalities between people in London who were getting sick. He discovered that ill people were getting water from the same Broad Street pump. Before Snow's work, the prevailing theory was that bad air sickened individuals instead of cholera-causing bacteria in the water.

The wonderfully named Vibrio diabolicus is a cousin of the cholera-causing bacterium

This bacterium, which belongs to the same genus as the cholera bacterium, was initially isolated from deep-sea hydrothermal fields. It was sampled from water that was scooped up during a French-American cruise in October 1991.

A French Army surgeon discovered that malaria is a parasitic disease in 1880—but scientists were initially skeptical

Charles Louis Alphonse Laveran won the Nobel Prize for his work "on the role played by protozoa" in causing diseases. His work included discovering and reporting the malaria-causing parasite in the blood of a patient suffering from malaria.

The history of germ theory, which explains that illnesses are caused by microorganisms

For centuries, the miasma theory, which held that illnesses were caused by clouds of "bad air" produced by decaying organic matter, was the accepted explanation for the spread of disease. The development of microscopes and the subsequent technology to isolate bacteria and test disease spread in mice greatly contributed to contagionists overturning miasmatists.

Cholera can persist in the environment, unlike smallpox, which needs a human host

Vibrio cholerae is the pathogen that causes cholera. It can reproduce in the environment without a human host, which means it's formally called a facultative pathogen. Obligate pathogens need a host to reproduce. Examples of obligate-based diseases include leprosy and smallpox.

The virus was officially described for the first time in 1789

Michael Underwood, an English physician and surgeon, was the first to describe the disorder, noting it caused disability in the lower extremities in children. Large-scale outbreaks of the disease were not observed until the late 19th century.

Penicillin was discovered by accident

In 1928, Alexander Fleming returned from vacation to find mold contaminating a petri dish of bacteria. Around the mold, the microbes had died—an accidental observation that led to the discovery of penicillin.

Historically, cholera has repeatedly disrupted the Hajj for Muslims

Outbreaks of the disease throughout the 19th century and the beginning of the 20th, killed thousands of religious pilgrims as they sought to complete this obligatory pilgrimage.

Before discovering cells, life was believed to emerge suddenly from inorganic matter

Popularized by Aristotle in the 4th century BCE, spontaneous generation was used to explain phenomena like mice appearing in seemingly sealed grain storage. The invention of the compound microscope in the late 16th century led to the identification of cells as the basic unit of life, but it was not until 1855 that their origin from preexisting cells was established.

Recent research indicates leprosy was present in the Americas before European settlers

New research published in 2025 upended long-held notions that the disease was introduced to the Americas by European colonizers. Evidence of a lesser-known leprosy-causing bacterium was found in ancient human remains that date back 4,000 years.

In 1933, the influenza virus was first identified through “ferret flu” experiments

In 1933, British researchers dripped filtered nasal fluids from a sick colleague into ferrets, which quickly developed “ferret flu.” This experiment proved influenza was viral, not bacterial, and established the basis for modern flu vaccines.

The pharmaceutical industry evolved, in part, from the discovery of synthetic dyes

In 1856, a chemist accidentally discovered mauveine, the world’s first synthetic dye, while trying to make quinine to treat malaria. The synthetic dyes that followed helped reveal germs under microscopes, paving the way for modern imaging techniques and breakthrough treatments, such as antibiotics.

Paris and Boston were redesigned partly to combat cholera's spread

Georges-Eugène "Baron" Haussmann, who oversaw Paris's redesign in the 1800s, replaced many of the city's narrow streets with wide boulevards. This was done at least in part to bring more air and light into the city to help control cholera. Architect Arthur Gilman redeveloped Boston's Back Bay to similarly combat cholera, among other reasons.

The discovery of the first extremophile and how it revolutionized DNA analysis

While investigating samples taken from within and around the hot springs at Yellowstone National Park, microbiologist Thomas Brock discovered Thermus aquaticus, a microorganism that thrived in hot water. It contained an enzyme called Taq polymerase, a critical molecule in polymerase chain reaction—a molecular photocopier that amplifies genetic signals to improve medical diagnostics.

Diphtheria was once a leading childhood killer before antibiotics and vaccines

In 18th- and 19th-century outbreaks, some New England families lost as many as eight children to diphtheria, and fatality rates in hospitals often topped 60%. The invention of antitoxins, penicillin, and vaccines dramatically reduced deaths.

The first major norovirus outbreak sickened half an elementary school

In 1968, 50% of an Ohio school got ill from this foodborne pathogen. The disease name is a nod to that original strain discovered in Norwalk, Ohio, when half the elementary school students became ill. Almost all kids reported nausea and vomiting. Everyone recovered.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

Poison ivy was sent to Europe in the 1600s as an exotic, ornamental oddity, where it was purposefully grown in the English royal gardens at Kew, the Faculty of Medicine in Paris, and a few other locations.

Validation of the greenhouse effect may have been misattributed

Although Irish physicist John Tyndall showed in 1859 that water vapor and carbon dioxide could absorb and radiate infrared radiation, experiments by American scientist Eunice Foote three years earlier identified the same phenomenon for light in general. Historically overshadowed, her work was rediscovered by female historians over a century later.

Poison ivy was sent to Europe in the 1600s as an exotic, ornamental oddity

The plants were grown in the English royal gardens at Kew, the Faculty of Medicine in Paris, and a few other locations.

Michael Sveda discovered cyclamate by accident

When this lab researcher brought his hands to his lips to smoke his cigarette in 1937, he tasted something sweet, which he called cyclamate. It was quickly used in diet sodas, but it was banned from the US in 1969 after being linked to rodent bladder cancer in lab experiments.

Grosse Île, the quarantine island of the Port of Quebec

As tens of thousands of Irish emigrated to North America to escape the Great Famine in the mid-19th century, many port cities set up quarantine areas amid an epidemic of cholera. In Quebec City on the St. Lawrence River, one island became a mass graveyard where over 3,000 Irish immigrants died over a decade as they waited in quarantine. Listen to the history here.

During the COVID-19 pandemic, readers returned to Camus' 'The Plague'

The 1947 novel, about a city in Algeria that enacts a city-wide quarantine to battle a deadly outbreak, captured readers' attention in the early months of 2020. In the UK, over 2,000 copies of the book were sold in March of that year, over six times what it had sold the month before.

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

In 1915, workers recovered a submarine-like vessel from the Chicago River, prompting fears of German espionage

The Curies developed a way to measure radioactivity in an old medical dissecting room

Despite lacking proper laboratory conditions, Marie and Pierre built an ionization chamber and a piezoelectric quartz electrometer to measure the amount of charged particles released by radiation, with a sensitivity of ten-trillionth of an ampere. Substances with different emission rates indicated different elements.

Ebola species have historically been named after where they were discovered, stigmatizing residents who live there, including Bundibugyo, in Uganda.

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

The concept of phantom limbs, the perception that amputated limbs are still present, dates back to a French military surgeon in the 16th century.

Against his wishes, Albert Einstein's brain was removed before his cremation, and the pathologist responsible stored it for decades in mason jars within a beer cooler.

Learn more about the history of fireworks, which dates back to an accidental invention during an alchemist's quest for information about immortality.

Human-to-human transmission of hantavirus remains extremely rare, so the 2026 hantavirus cruise ship outbreak doesn't mean we're facing a COVID-style pandemic risk.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Elk Cloner, the first computer virus to spread in public, was written as a practical joke by Richard Skrenta, a Pittsburgh high school student.

The term 'algorithm' originated from the Latinized name of al-Khwārizmī, a 9th-century mathematician whose works introduced Arabic numerals and the decimal-based numeral system to Europe and whose treatise 'Al-Jabr' gave algebra its name.

Louisiana's 'Cancer Alley' is infamous for having some of the highest industrial pollution, toxic air emissions, and cancer risks in the US.

The first horror movie is believed to be George Méliès' 1986 short 'The Haunted Castle,' which pioneered the use of special effects

The original copy of the Declaration of Independence is not a pristine document, and even features a smudged anonymous handprint in the bottom left corner.

Coral reefs get their colors from zooxanthellae—microorganisms that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.

The US first hosted the World Cup in 1994, a tournament that lives in soccer infamy for its poor planning and the murder of Colombian player Andres Escobar, who'd accidentally scored on his own net.

Watch a 1934 short film starring jazz legend Cab Calloway, a major figure in the Harlem Renaissance's music scene

Lesser-known phobias include turophobia, or the fear of cheese, and nomophobia, the fear of being without your cell phone.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Famed poet TS Eliot rejected the manuscript for George Orwell's political fable 'Animal Farm,' writing that its criticism of authoritarianism was not 'the right point of view.'

One of the most famous portraits ever taken is 'Afghan Girl' (1984) by Steve McCurry, yet the subject Sharbat Gula went much of her life without being identified or benefitting from the image's success.