Dear Science,

A few sex experts insist that even if a cure for HIV were
discovered tomorrow, we could never return to the days of unprotected
sex with tons of random, anonymous strangers in clubs like the
Mineshaft, because a new deadly STD would arise. I don’t think this is
so. There have been two truly deadly pandemic STDs: syphilis and HIV.
Both are horrifying, but syphilis has evolved from a disease that
killed in months to one that kills in decades, which makes sense. HIV
might take the same path. So in the whole of human history, we have two
deadly pandemic STDs, one that arose relatively recently and one that
was around in South America for God knows how long before Europeans
publicized it by dying from it in huge numbers. Even were we to assume
that syphilis was brand-new in 1494, that would still be roughly 500
years between the emergence of these two. I assume that more STDs will
evolve (it is a fine method of transmission), but why would it be
likely that they’d be worse than gonorrhea or herpes?

Bedroom Evolutionist

Nothing in life is as motivating as a parasite, particularly a newly
met parasite. The meeting can go down one of two broad paths. The first
is an ever-escalating battle, with host and parasite devising
newer and stronger defenses and attacks. The end of this interaction is
extinction—for the parasite or for the parasite and host both.
Rarely, if ever, do human parasites stick on this road for long. The
human immune system is the fucking monster of the natural world. Think of it this way: Each of us alive today survived multiple
massive pandemics. We’re the progeny of the handful who lived through
the plague and smallpox. Thank you, filthy, filthy human
civilization!

The other path is for the parasite to become as benign to the host
as possible—to be commensal. This is the hide-under-the-rug
strategy. If the parasite can get in and do its thing with so
little damage that the host doesn’t even notice it, this is great for
both.

Let’s think about those dizzy moments you mentioned, when the human
genetic pool met a new parasitic species. HIV is closely related
to SIV in primates. In primates, SIV is commensal—most primates
don’t even notice having it. So HIV is simply a parasite that went down
the first path; whereas SIV is a parasite that went down the second
path.

Science cannot predict the future for you. A new STD, just by
random chance, might start off rearing for a fight and start on the
death-spiral path. Or it might creep in, silently commensal as it
spreads in the population. Thanks to the (ongoing) HIV pandemic and the
continuing consequences, many more people might try to sit on the
sidelines and not discover firsthand which path the next parasite will
take.

Collaboratively Yours,

Science

Send your science questions to dearscience@thestranger.com

Jonathan Golob is an actual doctor.

3 replies on “Dear Science”

  2. Syphilis and HIV are not parasites. Syphilis is a bacterium; HIV is a virus. Parasites are highly-adapted, usually species-specific, eukaryotic organisms whose sophistication makes bacteria & viruses look like kindergartners (albeit with biological napalm).

  3. to 2, i think science was using the term “parasite” in the sense that only one party is benefiting from the interaction; in the case of HIV and a human victim, the HIV virus benefits from infection, and the human, obviously, does not. the term “parasite” can just refer to organisms that interact in a parasitic way with their host (as opposed to organisms that interact with their host in a commensural way, e.g.)

Comments are closed.