50 Fun Facts About Infectious Diseases

Which is the only human disease ever to have been eradicated?

The last natural case was a Somali cook, Ali Maow Maalin, in October 1977; the WHO certified eradication in 1980. Rinderpest, eradicated in 2011, is a cattle disease.

Edward Jenner's first vaccination in 1796 used material from which animal disease?

He scraped pus from milkmaid Sarah Nelmes, who had caught it from a cow called Blossom, and inoculated eight-year-old James Phipps. Blossom's hide hangs in a London medical school.

The word 'vaccine' derives from the Latin for which animal?

Jenner coined Variolae vaccinae, 'smallpox of the cow', for cowpox. In 1881 Pasteur proposed extending the term to all protective inoculations in Jenner's honour.

Which 9-year-old, mauled by a rabid dog, received Pasteur's rabies vaccine in July 1885?

The vaccine itself had been produced by Pasteur's colleague Émile Roux. Meister survived and later worked as a caretaker at the Pasteur Institute.

Robert Koch's 1876 discovery of the bacterium causing which disease is considered the birth of modern bacteriology?

He went on to identify the tuberculosis and cholera bacteria too, and won the 1905 Nobel Prize for his TB work.

How many criteria make up Koch's postulates for linking a microbe to a disease?

Koch and Friedrich Loeffler formulated them in 1884. They have largely been superseded by the Bradford Hill criteria and molecular versions.

Before germs were understood, which rival idea blamed disease on 'bad air'?

Galen's miasma theory dominated European medicine for centuries, even though the Roman writer Varro had speculated about invisible 'minute creatures' in 36 BC.

John Snow traced an 1854 cholera outbreak in London's Soho to what?

His map of deaths around the Broad Street pump was the first recorded piece of epidemiological tracking. He was also a pioneer of anaesthesia and gave Queen Victoria chloroform.

Cholera is an infection of the small intestine by which bacterium?

Some genetic strains, like the one in Haiti's 2010 epidemic, can kill within two hours of the first symptoms. The disease still causes up to 130,000 deaths a year.

Ignaz Semmelweis cut childbed fever deaths in 1847 by making doctors do what?

Doctors' wards at Vienna General Hospital had three times the mortality of the midwives' wards. Ridiculed, he died in an asylum of a gangrenous wound.

Which bacterium caused the Black Death?

Spread mainly by flea bites, it killed up to half of Europe's population between 1346 and 1353. The continent did not recover its numbers until the 16th century.

Which form of plague infects the lungs and spreads between people through the air?

Bubonic plague swells the lymph nodes and septicemic plague infects the blood, turning tissue black. Both are usually caught from fleas or infected animals.

The 1918 pandemic was misnamed 'Spanish flu' because of what?

Wartime censors in combatant nations suppressed bad news, while neutral Spain reported freely. The earliest probable cases were in Haskell County, Kansas.

Roughly how many people, about a third of humanity, were infected in the 1918–1920 flu pandemic?

The culprit was an H1N1 influenza A virus. Death estimates range from 17 million to 100 million.

In flu strain names like H1N1, what do the H and N stand for?

They are the two antigenic proteins on the viral envelope of influenza A. There are four types of flu virus in all: A, B, C and D.

In 2024, which disease was the leading cause of death from a single infectious agent worldwide?

It infected an estimated 10.7 million people and killed 1.23 million. Historically called consumption, it has been found in Egyptian mummies from 3000 BC.

Which vaccine, named after two French scientists, protects against TB?

Bacillus Calmette-Guérin is a weakened strain of bovine TB. The disease itself is caused by Mycobacterium tuberculosis.

Malaria is caused by single-celled parasites of which genus?

They are spread by female Anopheles mosquitoes and multiply in the liver, each infected cell eventually holding up to 40,000 parasites.

About what share of malaria cases and deaths occur in sub-Saharan Africa?

In 2024 some 282 million cases caused roughly 610,000 deaths. Treatment guidelines require two drugs in combination, one derived from artemisinin.

Dengue fever is chiefly spread by mosquitoes of which genus?

Aedes aegypti is the main culprit, with the Asian tiger mosquito A. albopictus also involved. More than 5 million infections were reported in 2023.

Roughly how many deaths do mosquito-borne illnesses cause each year?

Nearly 700 million people catch a mosquito-borne disease annually, making the insect the deadliest animal on Earth by a wide margin.

Jonas Salk announced a successful vaccine against which disease in April 1955?

He declined to patent it so it could be distributed widely; lawyers had concluded it was not patentable anyway. Albert Sabin's oral vaccine followed.

As of the mid-2020s, which two countries remain endemic for wild poliovirus?

Cases fell from an estimated 350,000 in 1988 to just 30 confirmed in 2022. The iron lung that once filled polio wards is now essentially obsolete.

What was the negative-pressure ventilator used for polio patients commonly called?

Patients typically needed it for one to two weeks during acute infection, though some lived inside one for decades.

Alexander Fleming discovered penicillin in 1928 as a crude extract of which mould?

He noticed it on returning from a Suffolk holiday to his untidy lab at St Mary's. Florey and Chain purified it in 1940 and shared his 1945 Nobel Prize.

Who shared the 1945 Nobel Prize in Medicine with Fleming for penicillin?

Howard Florey and Ernst Chain's Oxford team isolated the purified compound in 1940, turning a lab curiosity into a drug that could be mass-produced.

Prontosil, the first systemically active antibacterial drug, was developed in 1932–33 by a team led by whom?

It was the first sulfonamide, made at Bayer. Domagk famously used it to save his own daughter from a streptococcal infection.

The WHO estimates bacterial antimicrobial resistance directly caused how many deaths in 2019?

It contributed to more than 4 million further deaths in 2021. Multidrug-resistant microbes are nicknamed superbugs, and the WHO warns of 10 million deaths a year by 2050.

HIV belongs to which class of virus?

Retroviruses copy their RNA into the host's DNA. With antiretroviral treatment started early, life expectancy is now close to normal.

Roughly how many deaths has AIDS caused worldwide since it was first identified?

About 40.9 million people were living with HIV in 2025, and 1.2 million acquired it that year. HIV jumped to humans from other primates early in the 20th century.

Ebola was first reported in which year?

It is named after a river in what was then Zaire. The largest outbreak was the 2013–16 West African epidemic.

Which animals are believed to be the natural host of Ebola viruses?

They carry the virus without falling ill. Antibodies to Zaire and Reston strains have even turned up in fruit bats in Bangladesh.

Rabies was historically called hydrophobia because of what symptom?

Painful throat spasms when swallowing make patients panic at the sight of water. Rabies still kills about 59,000 people a year, 40 percent of them children.

Jeanna Giese survived symptomatic rabies in 2004 thanks to which experimental treatment?

Doctors put the Wisconsin teenager into a chemically induced coma in 2004. Only around fourteen people have ever survived rabies after symptoms began.

The commonly cited basic reproduction number (R0) for measles falls in what range?

That makes it one of the most contagious human pathogens. Deaths fell from 2.6 million in 1980 to 73,000 by 2014 thanks to vaccination.

If a disease has a basic reproduction number of 10, what is its theoretical herd immunity threshold?

The formula is 1 minus 1/R0, so a disease with R0 of 2 needs only 50 percent immunity to stop spreading.

Tetanus, caused by Clostridium tetani, is commonly known by what name?

The bacterium lives in soil, dust and manure, and the disease often begins with spasms in the jaw muscles. Hippocrates described it in the 5th century BC.

'Typhoid Mary' Mallon worked in which job while unknowingly infecting people?

The Irish-born cook was the first person in the US identified as an asymptomatic carrier of Salmonella Typhi, and was quarantined until her death in 1938.

Leprosy is also known as Hansen's disease, after a physician from which country?

Gerhard Armauer Hansen identified Mycobacterium leprae in 1873. Despite its reputation, leprosy is not highly contagious.

Lyme disease was first recognised as a separate condition in 1975 in which US state?

It takes its name from the town of Lyme. Spread by Ixodes ticks, it is the most common tick-borne disease in the Northern Hemisphere.

What is the name of the expanding red rash that is the most common sign of Lyme disease?

It appears at the bite site about a week later. A vaccine called LYMERix was withdrawn in 2002 for lack of demand.

Syphilis is caused by which bacterium?

Related Treponema bacteria cause yaws and pinta. The preferred treatment is still an injection of benzathine benzylpenicillin.

A prion is an infectious agent made of what?

It induces normal copies of the same protein to misfold. Stanley Prusiner coined the word in 1982 from 'proteinaceous infectious particle'.

What proportion of known human infectious diseases are zoonotic, meaning they come from animals?

For emerging diseases the figure rises to as much as 75 percent. Ebola, HIV and SARS are all linked to contact with wild animals.

Letters laced with Bacillus anthracis spores killed five people in which country in 2001?

Letters containing spores killed five people. Japan's Aum Shinrikyo had attempted an anthrax attack in 1993, and Unit 731 used it in WWII.

Rinderpest, declared eradicated in 2011, was a disease of which animals?

The German name means 'cattle plague'. Its last confirmed case was in Kenya in 2001, making it the second disease ever eradicated after smallpox.

Dracunculiasis, on the verge of eradication, is better known as what?

Only 10 to 15 human cases a year are now reported worldwide. The worm emerges through a burning blister over days and must be slowly wound out.

On what date in 1948 was the World Health Organization established?

The date is now World Health Day. The Geneva-based agency formally began work on 1 September that year.

How long does the WHO say you should wash your hands to remove most germs?

The CDC agrees that scrubbing with soap for 20 seconds works regardless of water temperature. Semmelweis would have approved.

Who brought the Turkish folk practice of inoculation against the pox to Britain in 1721?

Variolation deliberately infected people with a mild form of smallpox. Jenner's safer cowpox method replaced it 75 years later.