The 1918 influenza pandemic was one bad mamajama. By the time it was over (late 1919), 3-5% of all humans on the planet (as opposed to those out in space) had been killed by it.
The fatality rate was about 5% (meaning 5 out of every 100 infected people died); if you compare that Ebola (where 90 of every 100 infected people will die) that doesn’t sound all that bad, but consider that over 25% of the population had been infected by 1919 whereas only about 1 ten millionth of the human population has ever been infected with Ebola (dividing total # of Ebola cases – 1850 by the population of the planet in about 1999 – 6 billion). That’s Bad to the Bone.
It turns out that the 1918 pandemic wasn’t just one but three. Three successive waves of death – one in early 1918, one in late 1918 and one in early 1919. The second was by far the more deadly; no one is quite sure why. There are two leading hypotheses: (1) the virus changed between the first & second waves to become more deadly or (2) these were completely different influenza viruses from the begining. Definitively answering these questions is hard because this virus isn’t the most stable, so unless your left with digging up bodies and hoping for the best. Here is where the lungs come in.
A recent study in Lancet Infectious Disease looked at some preserved lung samples from sailors in the US Navy. Because the Navy keeps good records, we know which samples came from men who were infected in the first wave, second wave or both- and where their ships were. By comparing these two groups and the lung damage caused by each wave, this study concludes that the first & second waves were caused by different influenza viruses. If true, why would 2 deadly viruses pop up one right after the other? Why viruses like this come and go in the human population is an important question (Viral Ecology, if you will) This isn’t a virus I followed closely back in the day when I kept up with the literature. Aside from knowing the basics of influenza and its relatively recent graduation as undead, I am woefully ignorant. And who can blame me? When recent studies showing wild versions of the virus that are just fine with a deletion of the genes that you spent 6 1/2 years studying to get your PhD, you would be busy eating gallons of ice cream too*. I sense a good second post, as a other studies looking at preserved tissue from WWI Army soldiers comes to the opposite conclusion.
* – somewhat of a dramatic overstatement: my truly favorite genes and the promoter that drives them are still there.