49 Fun Facts About Infectious Diseases

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

Smallpox is the only human disease eradicated: the last natural case was a Somali hospital worker, Ali Maow Maalin, in October 1977, and the WHO certified eradication in May 1980.

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.

Which bacterium causes whooping cough?

Bordetella pertussis causes whooping cough, named for the gasping 'whoop' as a patient inhales after a coughing fit; the P in the DTaP vaccine stands for pertussis.

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

Joseph Meister, bitten by a rabid dog in Alsace, received Pasteur's series of injections from 6 July 1885, survived, and later worked as a caretaker at the Pasteur Institute in Paris.

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

Anthrax was the disease: in 1876 Koch cultured Bacillus anthracis and traced its spore-forming life cycle; he later identified the TB and cholera bacteria 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?

Four criteria make up Koch's postulates, first set out by Koch and Friedrich Loeffler in 1884 and restated by Koch in 1890; Stanley Falkow's 1988 molecular Koch's postulates later adapted them for genes.

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

Miasma theory held that rotting matter gave off a poisonous 'bad air'; it dominated European medicine into the 19th century, even though the Roman writer Varro had speculated about invisible disease-causing 'minute creatures' around 36 BC.

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

Vibrio cholerae produces a toxin that floods the small intestine with fluid, causing watery diarrhoea that can kill an untreated patient within hours; oral rehydration salts cut the death rate below 1%.

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

Wash hands in chlorinated lime was his order at Vienna General Hospital, where the doctors' ward had roughly three times the maternal mortality of the midwives' ward; ridiculed, he died in an asylum in 1865 of a septic wound.

Which bacterium caused the Black Death?

Yersinia pestis, spread mainly by the bites of infected fleas, caused the Black Death, which killed perhaps a third to a half of Europe's population between 1346 and 1353.

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

Pneumonic plague infects the lungs and passes person to person in coughed droplets, unlike bubonic plague, which swells the lymph nodes, and septicemic plague, which infects the blood; both of those are caught from fleas or infected animals.

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

Spain's press was not censored, since Spain was neutral, so its papers reported the outbreak freely while wartime censors in the combatant nations suppressed the news; the earliest well-documented cases came from Camp Funston, Kansas, in March 1918.

Roughly how many people were infected in the 1918–1920 flu pandemic?

500 million people, about a third of the world's population at the time, are estimated to have been infected by the 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?

Haemagglutinin and neuraminidase are the two surface glycoproteins on the envelope of influenza A; 18 H subtypes and 11 N subtypes are known, and the flu virus types are A, B, C and D.

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

Tuberculosis was the leading infectious killer in 2024, with an estimated 10.7 million cases and 1.23 million deaths; historically called consumption, it has been detected in Egyptian mummies from around 3000 BC.

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

BCG, Bacillus Calmette-Guérin, is a live weakened strain of Mycobacterium bovis developed by Albert Calmette and Camille Guérin at the Pasteur Institute in Lille and first given to a human in 1921.

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

Plasmodium parasites, chiefly P. falciparum and P. vivax, are injected by female Anopheles mosquitoes and multiply first in the liver, where a single infected cell can release tens of thousands of parasites into the blood.

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

About 95% of malaria cases and deaths occur in sub-Saharan Africa, with children under five accounting for most deaths; first-line treatment is an artemisinin-based combination of two drugs.

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.

Which virus causes chickenpox and, on reactivation, shingles?

Varicella-zoster virus causes chickenpox on first infection, then lies dormant in nerve ganglia and can reactivate decades later as the painful rash of shingles.

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

Polio was the target: Salk's killed-virus vaccine was declared safe and effective on 12 April 1955, and he declined to patent it; Albert Sabin's oral vaccine followed in the early 1960s.

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

Pakistan and Afghanistan were the only countries where wild poliovirus transmission had never been interrupted as of the mid-2020s; global cases fell from an estimated 350,000 in 1988 to a few dozen a year.

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

The iron lung, a sealed tank that breathed for a paralysed patient by cycling the air pressure around the body, was usually needed for one to two weeks, though some patients lived inside one for decades.

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

Penicillium rubens, long recorded as Penicillium notatum, was the mould Fleming found contaminating a staphylococcus plate at St Mary's Hospital in September 1928 after returning from a Suffolk holiday.

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?

Gerhard Domagk led the Bayer team that made Prontosil, the first sulfonamide; he used it to save his own daughter from a streptococcal infection and was awarded the 1939 Nobel Prize in Medicine.

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

1.27 million deaths in 2019 were directly attributable to bacterial antimicrobial resistance in the Lancet GRAM analysis cited by the WHO, which linked a further 4.95 million deaths to resistant infections.

HIV belongs to which class of virus?

Retrovirus is HIV's class: it uses reverse transcriptase to copy its RNA genome into DNA that is then inserted into the host cell's chromosomes, which is why the infection cannot be cleared.

Roughly how many deaths had AIDS caused worldwide by the end of 2023?

42 million people are estimated to have died from AIDS-related illnesses between the start of the epidemic and the end of 2023; HIV jumped to humans from other primates in Central Africa early in the 20th century.

Ebola was first reported in which year?

1976 saw the first two recognised outbreaks, in Nzara in Sudan and Yambuku in Zaire, where the virus was named after the nearby Ebola River; the largest epidemic was in West Africa in 2013–16.

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?

Victims cannot swallow liquids without agonising throat spasms, so they panic at the sight of water, hence 'hydrophobia'; rabies kills an estimated 59,000 people a year, about 40 percent of them children.

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

The Milwaukee protocol, devised by Dr Rodney Willoughby at Children's Hospital of Wisconsin, put the 15-year-old into a drug-induced coma while her immune system fought the virus; she became the first known unvaccinated survivor of symptomatic rabies.

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?

90% is the threshold: the formula is 1 minus 1/R0, so 1 − 1/10 = 0.9, while a disease with an R0 of 2 needs only 50 percent immunity to stop spreading.

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

Lockjaw is the common name because the disease often begins with spasms of the jaw muscles; Clostridium tetani lives in soil, dust and manure, and Hippocrates described the disease 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?

Norway was the homeland of Gerhard Armauer Hansen, who identified Mycobacterium leprae in Bergen in 1873; despite its reputation, leprosy is not highly contagious and most people are naturally immune to it.

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

Connecticut is where the towns of Lyme and Old Lyme lie; a cluster of juvenile arthritis cases investigated there in 1975 gave the disease its name, and Ixodes ticks spread it across the Northern Hemisphere.

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

Erythema migrans, the bull's-eye rash, appears at the tick-bite site after roughly a week in most infections; a human Lyme vaccine, LYMERix, was withdrawn in 2002 for lack of demand.

Syphilis is caused by which bacterium?

Treponema pallidum is a spiral-shaped spirochaete; its relatives in the same genus cause yaws and pinta, and a single injection of benzathine benzylpenicillin cures early syphilis.

A prion is an infectious agent made of what?

A misfolded protein is all a prion is: it induces normal copies of the same protein to misfold in turn; Stanley Prusiner coined the word in 1982 from 'proteinaceous infectious particle' and won the 1997 Nobel Prize.

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

60% of known human infectious diseases are zoonotic, and about 75 percent of new or emerging ones are; Ebola, HIV and SARS all entered humans through contact with wild animals.

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

United States postal workers and others died when spore-laced letters were mailed to news offices and two senators in autumn 2001, killing five; Japan's Aum Shinrikyo had attempted a release of the same spores in Tokyo in 1993.

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

Cattle plague is the literal meaning of the German name; the last confirmed case was in Kenya in 2001, and the FAO and OIE declared it eradicated in 2011, the first animal disease ever wiped out.

Dracunculiasis is better known by what name?

Guinea worm disease is the common name: a metre-long female worm emerges through a burning blister over days and must be slowly wound out on a stick; the Carter Center has led the eradication drive since 1986.

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

7 April 1948 is the day the WHO's constitution came into force, marked each year since as World Health Day; the first World Health Assembly met in Geneva that June.

How long does the CDC say you should scrub your hands with soap?

At least 20 seconds of scrubbing with soap is the CDC's advice, about the time it takes to hum 'Happy Birthday' twice, and it works regardless of water temperature.

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

Lady Mary Wortley Montagu, wife of the British ambassador to Constantinople, saw variolation practised there and had her daughter inoculated in London in April 1721, helping the practice spread among the English elite.