Spanish Influenza killed completely healthy people

The argument

What distinguishes Spanish influenza from other pandemics, on this argument, is not only its scale but the pattern of who died. Influenza, and pandemics more broadly, generally kill at the two ends of life: the very old, whose bodies cannot withstand the illness, and the very young, whose immune systems have not yet developed. Deaths concentrate where resistance is weakest. Spanish flu did not follow that pattern. It killed almost indiscriminately, reaching people whose age and health would ordinarily have protected them entirely. The scale gives the pattern its weight. Around 500 million people were infected — a third of the world's population at the time — and 50 million of them died. The effect on average life expectancies was a reduction of roughly twelve years, a figure that only makes sense if the dead were drawn heavily from people who would otherwise have had decades ahead of them. That is precisely what the age distribution shows: many of those killed were between twenty and forty, in the years of life normally least at risk from influenza. The other half of the pattern is stranger still. While healthy adults died in large numbers, elderly populations were virtually unaffected, inverting the usual shape of an influenza pandemic entirely. One theory offered for this is prior exposure: the elderly had lived through the Russian flu pandemic at the end of the nineteenth century, and may have retained immunity from it that younger adults never acquired. Whatever the explanation, the effect was a disease that killed the population best equipped to survive it while sparing the one usually most vulnerable. Because it killed completely healthy people on this scale, the argument concludes, Spanish influenza is the worst pandemic in history.

Premises

Counter-arguments

Rivals note that 'worst pandemic' can be measured several ways, and on many of them Spanish flu is surpassed: the Black Death killed a far larger share of the world's population, smallpox killed vastly more people across its history, and the Plague of Justinian devastated the ancient Mediterranean. The unusual mortality curve that struck healthy young adults is a distinctive and terrible feature, they grant, but distinctiveness is not the same as being the worst; by deaths as a proportion of humanity, or by total lives lost over time, other pandemics have stronger claims.

Rejecting the premises

[Rejecting P3] Killing healthy young adults made Spanish flu distinctive, but distinctiveness is not the same as being the worst pandemic on any standard measure. [Rejecting C] By share of the world's population killed (the Black Death) or total deaths over time (smallpox), rival pandemics surpass Spanish flu, so its indiscriminate lethality does not settle 'worst.'