Cases in which an HIV-positive person is infected with more than one strain of the virus are more common than previously believed, Canadian and U.S. scientists said Monday at the XVI International AIDS Conference in Toronto, CanWest News Service/Vancouver Sun reports.

Researchers reported that eight so-called “superinfection” cases have been discovered among 57 HIV-positive women in Mombasa, Kenya.

According to the study, many of the women contracted a second strain of the virus within one year of their first infection, while other infections occurred up to five years after their first infection.

While it is unclear whether the risk of contracting multiple strains of HIV is as likely as being infected for the first time, data are “starting to suggest” that reinfection is a concern, Julie Overbaugh, associate program head at the Fred Hutchinson Cancer Research Center, said, adding that although the study is thought to be the largest of its kind, only 57 women were involved.

The findings might be significant for HIV-positive people who seek other HIV-positive people for unprotected sex because they might become infected with a different strain, Overbaugh said.

In addition, there also are indications that infection with multiple strains of HIV speeds the progression of the virus, according to CanWest News Service/Sun.

As a result, it is important that even partners who are both HIV-positive use safer sex practices to prevent the virus passing between them, according to Bill Cameron, a professor of medicine at the University of Ottawa and the Ottawa Hospital.

Related studies among sex workers in South Africa show that people who first test positive for the virus can have two different strains of HIV.

“It may be that they got them from one partner, but it looks like they probably got sequentially infected,” Overbaugh said.

The findings of the superinfection studies might have negative implications for HIV/AIDS vaccine development because current research aims to protect against a “natural HIV infection,” not a superinfection, according to CanWest News Service/Vancouver Sun.

With multiple strains of the virus, it not only could be mutating but also combining with other forms of the virus to produce a strain “that looks different from either one,” Cameron said (Kirkey, CanWest News Service/Vancouver Sun, 8/15).

Kaisernetwork.org