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02/22/2005 Archived Entry: "Gordon on 3DCR"

Gordon P., our resident expert on all things scientific, responds to my entry of yesterday on the new strain of HIV: 3DCR.

Gordon writes, I agree that the emergence of this strain almost certainly has nothing
to do with "crystal meth" use, but rather, it most likely has evolved as a selection-response to the widespread use of anti-viral drugs to combat AIDS, Because virtually all anti-viral drugs are basically just "growth inhibitors," they are most effective against the slowest growing, least aggressive strains of a viral disease, i.e., they preferentially select _against_ the least virulent strains of a viral disease. However, selecting against the slowest-growing, least aggressive strains is evolutionarily equivalent to selecting _for_ the fastest growing, most aggressive strains to predominate in the next generation. In effect, widespread use of anti-virals will have the unintended consequence of "breeding" a nastier, more vicious HIV virus --- the mechanism is very similar to the one that has caused many strains of bacteria to become resistant to all known forms of antibiotics, and several formerly "benign" species of bacteria to become virulent pathogens because the competitors that kept down their population have been removed... :-(

It is in fact natural for _most_ diseases to become _less_ virulent with time as they adapt to their primary host, rather than more virulent, because it is a "Bad Business Practice" for a parasite to kill or severely debilitate its host too quickly, since to do so would decrease the opportunities for future "Free Lunches" for its species. Highly virulent diseases are almost always either _recently emerged_ (and therefore have not yet had time to adapt to their host species), or else highly infectious and capable of infecting a broad spectrum of hosts (e.g., the Influenza virus), so that they don't need to be especially "picky" about where their next "Free Lunch" is coming from. STDs, which are usually _VERY_ difficult to transmit without intimate physical contact and highly selective with regard to their host species (since few species have sex outside their species!), almost necessarily fall into the former rather than the latter category --- and therefore tend to become _less_ virulent with time, not more virulent, absent some external factor selecting for virulence (such as widespread use of anti-viral drugs....).

(The most successful disease organisms are the ones whose infections are largely asymptomatic and relatively benign --- because then the infected host will take fewer steps to combat the disease, and other potential hosts will be less likely to try to avoid the infected individual...)

That the "cluster" of patients in which this strain was initial detected were not already taking anti-virals doesn't necessarily refute my hypothesis, since all that would be required would be for them to have had sex with someone who _was_ taking anti-virals which had selected for a fast-growing, aggressive strain of HIV; since these patients' infections would have started out with a population composed entirely of fast-growing, aggressive HIV viri, their condition would therefore be expected to rapidly progress to full-blown AIDS.

BTW, I would not be surprised if there is by now a flourishing "black market" in anti-viral drugs within the gay community, since doctors are not allowed to prescribe anti-virals "prophylactically" because their side-effects are too severe. If there are significant numbers of sexually active individuals who are "illegally" taking anti-virals in the belief that these drugs will "protect" them from infection, then the situation is closely analogous to the over-use of antibiotics: An environment that will selectively "breed" for drug-resistant strains of viruses... :-(