Influenza Trivia
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49 free Influenza trivia questions with answers — science & nature quiz, new questions added Oct 2026.
This influenza trivia quiz covers the flu as a disease, a virus and a piece of history. It opens with the basics that most people get roughly right: how long the incubation period is, how many virus types there are, what the H and N in H1N1 stand for, and which animals are the reservoir. From there it goes into the biology that decides each winter: antigenic drift and shift, mixing vessels, why the vaccine has to be remade every year, how the strains are chosen and why most doses are grown in chicken eggs. The second half is history. The first convincing pandemic in 1510, the German bacteriologist who blamed the wrong microbe in 1892, the discovery of the virus in the 1930s, the first vaccine in 1945, and the pandemics of 1918, 1957, 1968, 1977 and 2009 with their subtypes, origins and death tolls. It also visits bird flu in Hong Kong, the antiviral made from star anise, the H5N1 case fatality rate, and the Italian astrological phrase that gave the disease its name. For the deadliest outbreak of all, see our separate Spanish flu quiz. Every answer was checked against Wikipedia's articles on influenza, its vaccines, drugs and pandemics, and each question links to the page that establishes it. Fifty questions, free, with an explanation after every answer.
30 of 49 questions with answers and explanations. Play the quiz
Q 01How long after exposure do influenza symptoms typically begin?
About two days
About two days, within a range of one to four. Flu then tends to strike abruptly, where a cold usually creeps up with a runny or stuffy nose.
Q 02Which virus, unrelated to influenza, is the leading cause of the vomiting bug nicknamed 'stomach flu'?
Norovirus
Norovirus. True flu is an infection of the airways, and vomiting is uncommon in adults who catch it, though children with flu do sometimes get it.
Q 03Which animals are the primary reservoir of influenza A viruses?
Aquatic birds
Aquatic birds. Wild ducks can carry the virus in their gut without getting sick, and with a reservoir like that on the wing, the WHO calls eradicating flu impossible.
Q 04In 2024, H5N1 bird flu jumped species and began spreading through which US farm herds?
Cattle
Cattle. The virus passed between dairy herds in several states, and some farm workers caught it from the cows, mostly with mild symptoms; tests showed pasteurisation kills it in milk.
Q 05In the subtype name H1N1, what does the H stand for?
Haemagglutinin
Haemagglutinin. The protein is named for a lab quirk, its knack of making red blood cells clump together; on the virus it is the spike that latches onto the cells of the airway.
Q 06As of 2025, which two influenza A subtypes circulate in people as seasonal flu?
H1N1 and H3N2
H1N1 and H3N2. Today's H1N1 is the 2009 pandemic strain, which pushed the older seasonal H1N1 out of circulation and then settled in as an ordinary winter virus.
Q 07Flu subtypes H17 and H18 were first found in which Latin American animals?
Bats
Bats. CDC researchers sampling little yellow-shouldered bats in Guatemala in 2009-10 found a flu virus unlike any seen before; only 16 H types had been known until then.
Q 08Influenza B has no subtypes but two lineages named after which two places?
Victoria and Yamagata
Victoria and Yamagata. No Yamagata virus has been confirmed anywhere in the world since March 2020, so American flu shots dropped that lineage from the 2024-25 season.
Q 09Which influenza type causes seasonal epidemics but has never caused a pandemic?
Influenza B
Influenza B. It infects almost nothing but people, so it seems to lack the animal reservoir from which type A keeps drawing strains that no human immune system has met.
Q 10What kind of genome do influenza viruses have?
Segmented negative-sense RNA
Segmented negative-sense RNA. The genome comes in separate pieces, eight of them in types A and B, so two strains that infect the same cell can trade whole genes.
Q 11The 1918 flu virus was rebuilt in 2005 using genes recovered from a victim buried where?
In Alaskan permafrost
In Alaskan permafrost. Johan Hultin dug at the mass grave in Brevig Mission as a student in 1951 and found no live virus; he went back in 1997 and took frozen lung tissue that still held its genes.
Q 12What is the gradual build-up of mutations that changes a flu virus's antigens called?
Antigenic drift
Antigenic drift. Small copying errors pile up until the antibodies from an earlier infection or shot no longer recognise the virus, which is why a person can catch flu many times in a lifetime.
Q 13In which US city did an 'Anti-Mask League' form in 1919 to fight a flu mask law?
Q 21When does a person with flu typically start being infectious?
A day before symptoms
A day before symptoms. People shed the virus before they feel ill and for five to seven days afterwards, so staying home once you feel sick comes too late to stop every infection.
Q 22Most flu vaccines are manufactured by growing the virus in what?
Embryonated chicken eggs
Embryonated chicken eggs. In a method more than 70 years old, the virus is injected into fertilised hens' eggs, left to multiply for several days, then harvested from the fluid and killed.
Q 23How often does the WHO meet to choose flu vaccine strains?
San Francisco
San Francisco. The city had fined or jailed people caught barefaced in 1918, and when masks were ordered back the next January a league that counted doctors and a city supervisor among its members rallied against them.
Q 14Which farm animals are called flu 'mixing vessels' because they can catch both bird and human strains?
Pigs
Pigs. When a bird strain and a human strain infect the same pig they can swap genes and emerge as a new hybrid; the 2009 pandemic virus was a blend of swine, bird and human flu genes.
Q 15Which cell-surface molecule do influenza HA proteins bind to?
Sialic acid
Sialic acid. Human strains grip a form of it that lines the nose and throat, while bird strains prefer a form found deep in human lungs, which may be why bird flu passes so poorly between people.
Q 16Which common painkiller should children with flu avoid because of its link to Reye's syndrome?
Aspirin
Aspirin. Once parents in America and Britain were warned off giving it to feverish children in the 1980s, Reye's syndrome, a sudden swelling of the liver and brain, became very rare.
Q 17Which two bacteria most often cause secondary pneumonia after flu?
Streptococcus pneumoniae and Staphylococcus aureus
Streptococcus pneumoniae and Staphylococcus aureus. Follow-on infections like these, rather than the virus alone, are thought to have caused most deaths in the 1918 pandemic, before antibiotics existed.
Q 18The Liberty Loan parade of 28 September 1918, blamed for a huge flu outbreak, was held in which US city?
Philadelphia
Philadelphia. Some 200,000 people packed the route although flu had already reached the city; within days its hospital beds were full, and its death rate ended among the worst in the nation.
Q 19Up to how many respiratory deaths does the WHO estimate seasonal flu causes worldwide each year?
650,000
650,000 is the top of the WHO's range, which starts at 290,000. That is more than the CDC's highest estimate of deaths in the first year of the 2009 flu pandemic.
Q 20Which age group is considered the most efficient spreader of influenza?
Schoolchildren
Schoolchildren. They catch flu easily and carry it home, which is why Britain vaccinates schoolchildren partly to shield the babies and grandparents they live with.
Twice a year, once per hemisphere
Twice a year, once per hemisphere. Experts meet in February to pick strains for the northern winter and in September for the southern one, because making the vaccine takes about six months.
Q 24How are live attenuated influenza vaccines given?
Sprayed into the nose
Sprayed into the nose. The vaccine's weakened viruses are bred to multiply only at the cooler temperature of the nose, so they stir up immunity there without taking hold in the warmer lungs.
Q 25Which US president ordered a mass swine flu vaccination drive for a pandemic that never came?
Gerald Ford
Gerald Ford. In 1976 one recruit's death at an army base set off a drive that vaccinated more than 40 million Americans in under three months, until reports of a rare paralysis, Guillain-Barré syndrome, halted it.
Q 26Oseltamivir works by blocking which flu protein, the N in subtype names such as H1N1?
Neuraminidase
Neuraminidase. The enzyme cuts newly made viruses loose from the infected cell; with it blocked they stay stuck to the surface instead of spreading to fresh cells.
Q 27Under what brand name is oseltamivir sold?
Tamiflu
Tamiflu. Governments stockpiled it in 2005 against a feared bird flu pandemic, yet a 2014 Cochrane review found that it eased adults' symptoms only about 17 hours sooner.
Q 28Oseltamivir is made from shikimic acid, originally extracted from which plant?
Chinese star anise
Chinese star anise. The spice yields so little of the acid that the drug ran short when governments rushed to stockpile it in 2005, and makers turned to engineered E. coli bacteria to brew it instead.
Q 29Which flu antiviral from the 1960s later found a second use treating Parkinson's disease?
Amantadine
Amantadine. The second use outlived the first: flu viruses grew so resistant to the drug that it is no longer recommended against them, while Parkinson's patients still take it.
Q 30Before the flu virus was found in 1933, doctors had long blamed influenza on what kind of organism?
A bacterium
A bacterium. Richard Pfeiffer found it in the sputum of flu patients and blamed it for the disease; the mistake survives in its name, Haemophilus influenzae, though what it can cause is meningitis.