It must be folk memory of epidemics past that compels us, whenever someone in the vicinity sneezes, to say "God bless you!" or "Gesundheit!", writes Frank McNally.
Such verbal reflexes seemed to have evolved with the human immune system. Which may also be why, when we admit to feeling under the weather, others will always nod sympathetically and assure us: "There's a bug going round." There probably is, too, whether they have evidence of it or not. But I wonder if anybody told Albert Gitchell there was a bug going round when, 80 years ago this week, he reported to a military infirmary in Kansas, suffering from aches and pains and a 1030F temperature.
Gitchell was an army cook, about to become famous as the first recorded victim of the Spanish Flu - not that the disease had a name yet. Hundreds of other soldiers at Fort Riley soon followed him. The virus was in New York within days, and thereafter sailed to Europe with American troops bound for the front.
By the time it was done, it had killed at least 40 million people worldwide: more than the Great War, or the Black Death, or any other temporary scourge in human history.
In time, the disease would be given many different names - as if the right description might help cure it. In Britain it was known as "Flanders Grippe". The Germans, initially suspected of spreading it as a weapon, called it "Blitzkatarrh". French-speaking Switzerland seductively titled it "La Coquette". In parts of Asia, it was "Bombay Fever".
The definitive name came about by accident. Some of the worst outbreaks were in Madrid and Seville, and the King of Spain added to the flu's fast-growing infamy by nearly joining the list of fatalities. More to the point, being neutral in the war, Spain was free of the press censorship that restricted reportage of the pandemic elsewhere.
Thus it was that the disease came to be called "Spanish Lady" or, less poetically, Spanish Flu. The name quickly stuck, except in Spain: which, following the normal European practice of blaming problems on the neighbours, called it "French Flu", or the "Naples Soldier".
The virus reached Ireland in June 1918, and although its progress here was overshadowed by other events of that turbulent era, it is thought to have killed at least 20,000, making the War of Independence a minor affair by comparison. The Irish Times was soon reporting a "mysterious epidemic" sweeping the country and on July 1st carried a public health notice about "Spanish Influenza".
"One case today may mean 100 tomorrow and thousands within a week," warned the Local Government Board's chief medical officer, who also urged sufferers to minimise infection by taking "Formamint Tablets" - available from all chemists "at 2s/2d per bottle".
July 1918 was one of three terrible peaks of the disease in Europe, the last of which was February 1919. The one between, in October, carried off the Austrian expressionist painter Egon Schiele, aged 38, only three days after it had also claimed his pregnant wife, Edith. A week later, the French poet Guillame Apollinaire followed them, his constitution already weakened - like many of the flu's male victims - by war service.
Back in the US, around then, the army's surgeon general was profoundly affected by a scene he witnessed at a camp near Boston. "I saw hundreds of young stalwart men in uniform coming into the wards of the hospital," he wrote. "Every bed was full, yet others crowded in. The faces wore a bluish cast; a cough brought up the blood-stained sputum. In the morning, the dead bodies [ were] stacked about the morgue like cordwood." Chicago reported a 43 per cent drop in crime during October 1918, a fact directly attributed to the flu. But the improved law and order came at a high price throughout the US. That was the deadliest month in the country's history, with 195,000 dying from the virus. When San Franciscans took to the streets in November to celebrate the end of the war, they all wore face-masks, as ordered by health officials.
The reasons for the Spanish Flu's devastating power remained a mystery even into this century. But such had been its virulence that there was unease in parts of the scientific community when, a few years ago, Canadian researchers exhumed the body of a known victim - preserved in the Arctic permafrost - and recreated the virus in a laboratory.
When they infected monkeys with the reconstructed flu, the results were startling. Symptoms appeared within 24 hours and the eventual destruction of lung tissue was so extensive that, had the animals not been killed humanely, they would have drowned in their own blood. A key finding of the experiments was that the immune system's response, rather than the virus itself, did the damage.
You know a disease is serious when it inspires a popular children's rhyme. Yes, it is probably a myth that "Ring-a-ring o' roses" is an exercise in folk memory of the Black Death, or a subsequent outbreak of plague. But in 1918, children had a new skipping rhyme: "I have a little bird/ Its name is Enza/ I opened the window/ And in flew Enza." Anyone who heard that knew there was a bad bug going round.