AIDSWEEKLY Plus; Monday, April 23, 2001
Michael Greer, Staff Medical Writer

NewsRx - The explosive HIV-1 epidemic in sub-Saharan Africa is unlikely to be the result of a viral subtype with increased infectivity, according to the results of a study published in the April 14, 2001, issue of the Lancet.

The HIV-1 epidemic in eastern and southern sub-Saharan Africa is mainly caused by HIV-1 subtypes A, C, and D, whereas those in the USA and Europe are mostly a result of subtype B, and that in Thailand of subtypes B or E. The probability of HIV transmission per sexual act (infectivity) is calculated by studying monogamous couples in which one partner is HIV positive and the other is HIV negative (HIV discordant couples).

Ronald H. Gray, of the Johns Hopkins School of Public Health, Baltimore, Maryland, and colleagues set out to calculate infectivity in 174 heterosexual, monogamous, HIV-1 discordant couples in Rakai, Uganda. This is an area in which this type of calculation has not been done before, and where infection is due to HIV subtypes A and D, the researchers said. They also aimed to work out whether factors such as age, viral load (amount of HIV-1 in the blood), and presence of sexually transmitted diseases (STDs) had any effect on infectivity.

Every 10 months between November 1994, and October 1998, the researchers collected data on frequency of sexual intercourse (as reported by each partner independently), viral load in the HIV-1 positive partner, HIV-1 status in the partner who was initially HIV-1 negative, and diagnosis of STDs.

The overall probability of transmission per sexual act was 0.0011, which was slightly higher than that previously found for US and European couples, but lower than for Thai couples, Gray et al. reported.

Infectivity increased with higher viral load and with genital ulceration (a symptom of STDs).

The researchers concluded that the explosive HIV-1 epidemic in Uganda is unlikely to have been caused by greater infectivity of subtypes A and D, and that measures to decrease viral load (e.g., antiretroviral drugs) would probably decrease infectivity in this population.

This article was prepared by AIDS Weekly editors from staff and other reports.

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