World War 1 ushered in an unprecedented wave of global mobility. And at its end, millions of people -- soldiers, refugees -- turned and headed for their homes. Some took with them a virulent strain of subtype H1N1 influenza, the same subtype as that causing the present alarm. It swept the world.
In two years "Spanish flu" (so named because it was first widely reported in Spain, which was not under wartime media censorship) killed between 50 million and 100 million people. By comparison, the war had taken 16 million lives in Europe, and, decades later, the AIDS pandemic killed 25 million over 25 years.
One in every five humans contracted the disease -- as many as half of those exposed to the virus. Of those, between two and 20% died (the usual mortality rate from influenza is more like 0.1%) and some populations suffered more grievously than others. Nearly a quarter of the population of Western Samoa died in two weeks.
In New Zealand, more than 8600 people died, with Maori particularly badly struck. At its height, the country virtually ground to a halt.
The most common mechanism of death was a cytokine storm, an response in which the body's immune system goes into a destructive feedback loop. Ironically, people with the most vigorous immune systems were the most likely to die this way. So while the very young and the very old were the most likely to survive, young adults were most likely to die.
Those young adults were often parents, and there are harrowing stories of children, orphaned by the disease, sitting watch over their dead parents. NZHistory.net has a number of oral history recordings from the New Zealand Sound Archives, including this one:
[Woman speaking] Ah no, the children were very good; we had to keep them—they were not allowed out the gate. They had to play in their own backyards. So, no, the children seemed to realise too how dreadful the time was. And the unfortunate part was when anyone having a baby, the mothers were lost, the babies seemed to survive. But there was a dreadful lot of babies were left without their mothers. And I think that was one of the saddest parts.
[Man speaking] At the school, when we're in the class, and that, some of my friends whose parents had passed away would all of a sudden start their crying, and the teacher would have to console them later.
So it was no wonder that, in 1976, the US government responded strongly to the news that 19-year-old Pvt. David Lewis had died after contracting, from an unknown source, a variant of the 1918 swine flu virus. About 500 soldiers at the base contracted the flu, continuing a historical congruence between H1N1 and the military.
On expert advice, President Gerald Ford commissioned the development and distribution of a vaccine that was eventually received by about 40 million Americans. Not one more person died of the flu. But, horrifyingly, about one in a thousand people inoculated against it developed an ascending paralysis called Guillain-Barré syndrome. By the time the vaccine was withdrawn at the end of the year, 500 Americans were suffering from the condition and 30 died as a result of receiving the vaccine. And yet, it may still be true that the mass-vaccination decision was not the wrong one.
So that's how high the stakes are. And if 80 people have died in Mexico, the new outbreak is already more serious than that of 1976. That clearly doesn't mean it's 1918 again. For one thing, we now have anti-viral drugs that appear to be effective against the latest strain. The new swine flu also does not appear to spread very rapidly amongst humans. But if you are wondering why the authorities are so excited, well, there's history there.