"End of the World" plague

I happened across this today and it inspired me to write a post I've been thinking about for a while. The link is to a story about the so-called Cyprian plague of the Third Century, possibly an outbreak of smallpox, which is said to have given a boost to Christianity.

A couple of decades back there was a virologist or epidemiologist, whose name I forget, who firmly predicted that at some time in the coming decades, an emerging infectious disease would explode and decimate the global population. He generated immense controversy in part because it kind of sounded like he was hoping for it, part of his premise being that there are too many of us. Unfortunately this story doesn't have parameters that make it easily researchable, so if anybody can remember who I'm talking about please let me know. Anyway . . .

The argument in favor of this scenario seems pretty convincing at first. There have been plenty of instances in the past in which infectious disease outbreaks have caused crashes in human populations, albeit limited geographically because not all populations were in contact. The Black Death is thought to have reduced the European population by50% or more late in the 14th Century. While it is not possible to prove historical causation, there is a compelling story that this event ultimately brought about the end of the Middle Ages and the emergence of modernity. A sudden shortage of labor, and the availability of twice as much land and fixed capital per person, raised the status of the peasantry and hastened the end of serfdom. The introduction of hitherto unknown diseases to the Americas, notably smallpox, caused the so-called Demographic Disaster which reduced the indigenous population by some 90% and made the European conquest complete.

HIV and the hemorrhagic fevers, SARS and MERS, although none of them turns out to be the apocalypse plague for various reasons, do prove that new human pathogens will continue to appear frequently. These particular viruses have limited transmissibility, which is why our global population continues to grow, but the point is, with every city on earth connected by air travel that can get an infectious person from Nairobi to New York in less than a day, when the new smallpox does arrive -- highly transmissible, highly lethal -- we're screwed, lassoed and tattooed.

Well, maybe. The most important difference is that today, we understand infectious disease. We'll know how to take effective action, both in the short term through isolation and quarantine, and in the longer term through understanding the pathogen and coming up with effective treatments and/or prophylaxis. We hope. But the deeper point is, you can't understand the future by extrapolation. Will there ever be 8 billion humans alive at one time? I wouldn't bet on it. This is only one reason.