50 Fun Facts About Epidemiology

John Snow pinned London's deadly 1854 cholera outbreak on which source on Broad Street in Soho?

A water pump on Broad Street was the source, and the parish disabled it by taking off the handle. Workers at the nearby brewery, who drank their beer allowance instead, never caught the disease.

Mary Mallon, better known as Typhoid Mary, infected dozens of New Yorkers while working in which job?

Cook to a string of wealthy families, Mallon carried typhoid without ever falling ill herself. She was forcibly quarantined in a hospital on New York's North Brother Island.

The 1918 flu pandemic was nicknamed after which neutral country, whose uncensored newspapers reported it freely?

Spain stayed out of World War I, so its press covered the outbreak while the warring nations censored the news. That made Spain look like the epicentre, though the flu did not begin there.

The word vaccine comes from the Latin for which farm animal, thanks to Edward Jenner's 1796 experiment?

Cow is 'vacca' in Latin, and Jenner's vaccine used cowpox, a mild infection caught from cattle, to guard against smallpox. His first subject was James Phipps, his gardener's eight-year-old son.

Quarantine takes its name from a Venetian word for how many days that plague-era ships had to wait in isolation?

40 days was the 'quarantena' that ships sat out before anyone could go ashore during the Black Death. It followed a 30-day isolation first imposed in 1377 by Ragusa, the modern Dubrovnik.

Ignaz Semmelweis slashed childbed fever deaths on a Vienna maternity ward by making medical staff do what?

Wash their hands in chlorinated lime, he insisted, and the death rate fell from 18% to under 2%. Offended colleagues mocked him, and he died in an asylum in 1865.

Florence Nightingale's 'rose' diagrams showed that soldiers in which war mostly died of disease rather than wounds?

Crimean War hospitals lost ten times more soldiers to illnesses such as typhus and dysentery than to battle wounds. Nightingale later became the first woman elected to the Royal Statistical Society.

Which term for an outbreak's first known case arose when a CDC code, 'O' for 'Outside California', was misread?

Patient zero was born when readers of a 1984 AIDS study took the letter O for a nought. The man so labelled, flight attendant Gaëtan Dugas, was not in fact the first American case.

James Lind's shipboard experiment on twelve sailors, one of the first clinical trials, showed that what cured scurvy?

Citrus fruit won: the pair of sailors given two oranges and a lemon each day did best, while cider, vinegar and seawater did little. Lind ran the trial as a naval surgeon in 1747.

Which term describes the indirect protection unvaccinated people gain once most of a community is immune?

Herd immunity was first named in 1894 by a US veterinary scientist describing well-fed hogs that resisted disease. It applies only to contagious infections that pass from person to person.

Which term describes a disease, like chickenpox in Britain, that is constantly present in a population?

Endemic diseases keep a steady, predictable number of people sick, and that number can be high or low. The word says nothing about severity: such a disease can be mild or grave.

Which epidemiology measure counts only the new cases of a condition arising in a population over a set period?

Incidence tracks new cases and so conveys the chance of contracting a disease, whereas prevalence shows how widespread the disease already is.

What name is given to an infectious disease, such as rabies or Ebola, that passes from animals to humans?

Zoonosis covers any infection that crosses from other animals to people, salmonellosis included. Most human diseases began in other species before making the jump.

John Snow gave Queen Victoria which anaesthetic during the births of her last two children, Leopold and Beatrice?

Chloroform was the Queen's own request in 1853, and Snow gave it again in 1857. He had studied the drug closely and warned that it needed far more careful dosing than ether.

Which ancient Greek, who blamed illness on four unbalanced humours, first linked disease to the environment?

Hippocrates, known as the father of medicine, sought a logic to sickness in people's surroundings. He also gave the word epidemic its medical meaning, using it as the title of a treatise.

Before germ theory, epidemics of cholera and plague were blamed on which noxious 'bad air' from rotting matter?

Miasma is Greek for pollution, and the idea lives on in the name malaria, medieval Italian for 'bad air'. Medicine abandoned it after 1880 as germ theory won out.

Which Nobel-winning physician gave his name to four postulates for proving that a microbe causes a disease?

Robert Koch published the refined criteria in 1890, six years after drawing them up with Friedrich Loeffler. Viruses later bent the rules, since many infect people without making them ill.

Ronald Ross won the 1902 Nobel Prize in Medicine for proving that malaria is carried by which insects?

Mosquitoes were confirmed as the culprits in 1897, when Ross found the malaria parasite in the gut of one he had dissected. His discovery laid the foundation for fighting the disease.

Legionnaires' disease was named after a 1976 outbreak among veterans at a hotel convention in which American city?

Philadelphia hosted the American Legion at the Bellevue-Stratford Hotel that July. The mystery pneumonia that followed led scientists to a bacterium nobody had identified before, Legionella.

The US Centers for Disease Control and Prevention grew out of a wartime malaria programme based in which southern city?

Atlanta was chosen because malaria was then widespread across the American South. In 1947 the agency paid Emory University a token $10 for the land where its headquarters was built.

Richard Doll and Austin Bradford Hill tied smoking to lung cancer by tracking 40,000 Britons in which profession?

Doctors replied in their thousands: 40,701 of them, two-thirds of those written to in 1951, sent back their smoking habits. The study went on following them for 50 years.

Which term for a trait that raises the odds of disease was popularised in 1961 by the Framingham Heart Study?

Risk factor entered the medical vocabulary through a 1961 paper from the study, which began in 1948 with 5,209 adults from one Massachusetts town and went on to enrol their children and grandchildren.

Which inactive treatment, named from the Latin for 'I shall please', is given to a clinical trial's comparison group?

Placebo treatments include sugar pills, saline injections and even sham surgery. Their dark twin is the nocebo, Latin for 'I shall harm', an inert substance that hurts because people expect it to.

What is the gap between catching an infection and the first symptoms, one to three days for a common cold, called?

Incubation period lengths vary enormously, from as little as half a day for cholera to as long as six weeks for glandular fever.

Which public health practice identifies everyone an infected person may have exposed so they can be tested or isolated?

Contact tracing aims to cut transmission by finding, testing and treating the people an infected person has met. It played a major role in Britain's handling of Ebola in 2014.

With a basic reproduction number estimated at 12 to 18, which childhood disease is among the most contagious known?

Measles spreads through the air on coughs and sneezes, and people are infectious from four days before the rash appears. One case in an unprotected community is expected to infect 12 to 18 others.

Rabies in the unvaccinated tops 99% on which measure, the share of people diagnosed with a disease who die of it?

Case fatality rate counts deaths only among people diagnosed, so statisticians note it is really a proportion rather than a true rate. It says nothing about how common the disease is.

Which type of study, like the Nurses' Health Study begun in 1976, follows a group over years to see who falls ill?

Cohort studies start with people who do not have the disease and watch to see who develops it. The Nurses' Health Study signed up 121,700 married registered nurses aged 30 to 55.

What term describes a trial in which neither participants nor researchers know who is getting the real treatment?

Double-blind trials keep both sides in the dark so that expectations cannot sway the results. An early example was the Nuremberg salt test of 1835, run by the city's top public health official.

Lyme disease is named after a town in which US state, where a puzzling cluster of childhood arthritis appeared in 1975?

Connecticut gave the disease its name when cases first taken for juvenile arthritis turned up in three towns, Lyme among them. The oldest known sufferer is Ötzi the Iceman, a 5,300-year-old Alpine mummy.

Jonas Salk declined to patent his vaccine against which disease, tested on about a million children in 1954?

Polio trial volunteers, about one million children, were known as the polio pioneers. When the vaccine's success was announced in April 1955, Salk was hailed as a miracle worker.

The World Health Organization, founded in 1948 as a United Nations agency, is headquartered in which European city?

Geneva houses the WHO, which also runs six regional offices and 150 field offices. World Health Day, 7 April, marks the date in 1948 when the agency's constitution came into force.

The Ebola virus, identified in 1976 after an outbreak at Yambuku in Zaire, is named after which kind of natural feature?

A river, the Ebola, gave the virus its name, though it was only at first thought to flow close to the outbreak. Reports conflict over whether an American or a Belgian researcher coined it.

The US Public Health Service's Tuskegee study left hundreds of Black men untreated for which disease from 1932 to 1972?

Syphilis went untreated in 399 men even after penicillin was in wide use by 1945, and they were told only that they had 'bad blood'. President Bill Clinton formally apologised in 1997.

Minamata disease, discovered in 1956 after a chemical factory fouled a Japanese bay, is poisoning by which metal?

Mercury built up in the fish and shellfish of Minamata Bay, which local families ate. Cats were struck so visibly that their illness was nicknamed dancing cat fever.

Walter Reed's US Army board in Cuba confirmed how which disease spreads, clearing the way to build the Panama Canal?

Yellow fever killed Reed's own assistant, Jesse Lazear, during the experiments in Cuba. Reed gave the credit for the idea his board confirmed to the Cuban scientist Carlos Finlay.

The first published randomised controlled trial in medicine tested the antibiotic streptomycin against which disease?

Tuberculosis was the proving ground in 1948 for streptomycin, isolated only five years earlier. One of the paper's authors, Austin Bradford Hill, is credited with conceiving the modern randomised trial.

Joseph Goldberger proved that pellagra, rife in the American South in the 1910s, was not infectious but caused by what?

A poor diet built on corn was the cause, and to show pellagra could not be caught, Goldberger injected himself, his wife and other volunteers with sufferers' blood. None of them developed it.

Lady Mary Wortley Montagu championed smallpox inoculation in Britain after seeing it practised in 1717 in which empire?

Ottoman practitioners scratched pus from a mild smallpox blister into a healthy person's skin, a method Montagu called engrafting. She had survived the disease in 1715, left with a disfigured face.

Ali Maow Maalin, the last person to catch smallpox naturally, fell ill in 1977 in which East African country?

Somalia's Ali Maow Maalin was a hospital worker who later said he had skipped his own smallpox jab because the shot looked painful. He made a full recovery and later gave vaccinations in another eradication campaign.

Which term describes a living carrier, such as a tick or a tsetse fly, that passes a pathogen to another organism?

Vector animals often feed on blood, picking up a pathogen at one meal and passing it on at another. Arthropods such as ticks, lice and biting midges make up a major group of them.

MERS, a coronavirus disease first identified in Saudi Arabia in 2012, typically reaches humans from which animals?

Camels pass the virus to humans directly or through respiratory droplets, though it is believed to have come originally from bats. Most infections have occurred in the Arabian Peninsula.

Which term, from the Greek for an infirmary, describes an infection picked up in a hospital or other care facility?

Nosocomial infections are a major killer: the CDC estimated roughly 1.7 million of them in American healthcare in 2002, contributing to some 99,000 deaths.

Which study design, often used for rare diseases, compares people who have a condition with similar people who do not?

Case-control studies scored a famous triumph when Richard Doll and Bradford Hill used one to link tobacco smoking with lung cancer. They are relatively inexpensive, and small teams can run them.

Which measure of a medical test, named in 1947, is the share of people with a disease who correctly test positive?

Sensitivity is what makes a negative result trustworthy: a highly sensitive test rarely misses people who do have the disease, so it is useful for ruling an illness out.

Which term names a third variable that influences both an exposure and an outcome, making a spurious link look causal?

Confounder variables help explain why correlation does not imply causation. Careful design, such as assigning people to groups at random, is needed to tell real effects from spurious ones.

Which London haberdasher's 1662 analysis of the Bills of Mortality has led some to call him the first epidemiologist?

John Graunt produced the first life table, giving the chances of surviving to each age, even though the death records he drew on listed no ages. His book won him a place in the Royal Society.

The surgeon Percivall Pott made the first link between a job and cancer in 1775 after studying which workers?

Chimney sweeps developed scrotal cancer from the soot they worked in, Pott found. He became the first person to tie a malignancy to a carcinogen in the environment.

Which Derbyshire village famously quarantined itself to stop a 1665 outbreak of bubonic plague reaching its neighbours?

Eyam villagers, led by their rector William Mompesson, cut themselves off as the outbreak ran its 14-month course, and by one account at least 260 of some 350 died. The infection came in a bundle of cloth from London.

Kuru, a fatal brain disease once common among the Fore people of Papua New Guinea, was spread by which funeral custom?

Cannibalism of dead relatives, meant to help free their spirits, passed on the prions behind kuru. Women and children usually ate the brain, where prions were most concentrated, so they were struck most often.