Monkey’s Viral Defense

To understand the broader background of Ebola and other viruses, read Michael Spector in the New Yorker. While his title “The Doomsday Strain” is overhype–in fact, I argue, these killer viruses are chronic population regulators–the world he describes, of eat and be infected, is the heart of what’s going on.

What’s unique about Africa is that, as the birthplace of humanity, it’s also the birthplace of the largest number of near-human species on our planet. The nearer-human you are, (1) the closer you compete; (2) the more pathogens–especially viruses–you share. Things like Monkeypox, a cousin of smallpox. Now that we no longer get smallpox vaccinations, monkeypox makes occasional forays into humans–and could evolve into a smallpox-like contagion.

How do viral pathogens evolve? A typical scenario:

–Virus propagates in an adapted host. Most viruses cause mild or no symptoms, because that way they keep their host around the longest. Humans are full of herpes-type viruses you never heard of–because we all have them, and they don’t cause illness.

–Virus jumps from adapted host to non-adapted host. Either the virus fails to grow at all–or else it grows too fast, killing the host before it can transmit to a new one.

–Either the virus burns out quickly in the new host, or it kills off 90% of them. If enough new host survive, they will evolve to adapt to the new virus. Like HIV–there are genetic variants of humans who don’t get AIDS. If this were the state of nature, without technology, these AIDS-resistant people would inherit the earth.

From the standpoint of population: How do viruses relate to their host?

One way they relate is that the virus defends its adapted host population from competitors. When two different monkey populations meet, individuals bite each other, copulate with each other (in secret, sleeping with the enemy), and share bodily fluids in every possible way. Without realizing, in effect they send each other their own viruses–adapted to the donor, possibly deadly to the recipient. In the long run, whoever best withstands the other’s viruses “wins.”

In Africa, an unfortunate effect of “civilized” development has been to increase human-monkey contact–most often by humans consuming near-human primates, aka “bushmeat.” But the bushmeat still sends us their viruses. For most of human history, these viruses helped hold Homo sapiens  population in check. Thanks to “civilized” medicine, they no longer do.

Or do they?