I’ve always held the view that HIV was becoming less deadly because deadly forms of viruses kill off their hosts more quickly and have less chance to replicate. But a study that’s just out refutes that and shows that in a controlled population (the military) they’re seeing HIV become more virulent as measured by how quickly after infection the person’s CD4 cells drop and they need to go on meds. [Additional discussion of the article is available elsewhere.]

Researchers studied data from more than 2,000 HIV-positive active-duty military personnel, retirees, and dependents between 1985 and 2007 who had tested HIV-negative within the previous four years. When they looked at patients’ first CD4 count after HIV diagnosis, they found that it decreased from an average of 632 cells/mm³ in 1985-1990 to 514 cells/mm³ in 2002-2007. Additionally, 25 percent of patients diagnosed with HIV in recent years already had fewer than 350 CD4 cells/mm3, the threshold for when antiretroviral therapy should begin, compared to only 12 percent of patients in the late 1980s.

The authors note that the trend seems to have stabilized, perhaps due to the widespread introduction of highly active combination antiretroviral therapy.

It suddenly struck me what the flaw was in my theory… Medications… Basically meds change everything and let people with virulent forms of HIV survive longer – as long as people with mild forms of HIV. But that’s not quite right either since when someone is “undetectable” they pretty much can’t pass on the virus. But perhaps the more virulent strains are exceptions to that rule? Or maybe we’re really talking about a small population of “gift givers” and the gift givers with the most aggressive strains are are more likely to have their “gifts” be “successful”…

The point is ARVs most likely changed the rules in this scenario and HIV may indeed becoming more virulent, not less.