HIV epidemic among homosexuals, drug users probably had different sources

WESTPORT, CT (Reuters Health) - Epidemiological evidence suggests that the HIV-1 epidemic in homosexuals and intravenous drug users in Western countries originated from different sources.

Dr. Carla Kuiken from Los Alamos National Laboratory in Los Alamos, New Mexico, and colleagues analyzed the relationship of various HIV-1 variants within subtype B (the most prevalent subtype in Western countries) in homosexuals and intravenous drug users in Sweden, Norway and Holland in an effort to understand how the epidemic might have spread.

In both Sweden and Norway, the two risk groups carried distinct HIV-1 variants, the authors report in the November issue of the American Journal of Epidemiology. Moreover, the mutations shared by Swedish and Dutch drug users were common, whereas those unique to each country were relatively rare.

Similarly, the sequences from Norwegian and Dutch homosexuals seemed to be indistinguishable, the researchers note.

"Differences between homosexual and intravenous drug user virus populations appear to be ubiquitous in Northern Europe," the authors conclude. "Based on the available data, the most plausible scenario seems to be that the subtype B virus was carried out of Africa and introduced into the Western homosexual community by one person."

The researchers postulate that the virus then spread to other risk groups in the U.S., where the virus evolved independently, remaining relatively homogeneous within the separate risk groups.

"Sequencing of more virus variants from a large number of U.S. intravenous drug users from different geographic locations would seem to be the best way to determine the plausibility of this scenario," they assert.