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Researchers Alarmed by Case of HIV 'Superinfection'

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Feb. 2, 2000 (San Francisco) -- The fate of a 40-year-old Canadian gay man could tell physicians a great deal about the future of the AIDS epidemic, particularly whether deadlier, drug-resistant strains of the disease might reinfect relatively healthy patients with devastating consequences. According to a case study presented here at a meeting of HIV researchers, the 40-year-old had been living with HIV since 1989 without taking anti-retroviral drugs, and then suddenly, his health began to deteriorate.

The amount of virus in his blood increased, and even a combination of anti-AIDS drugs didn't stop his decline. That made the man's physician suspicious that his patient might have been infected twice, the victim of a new 'superinfection' -- something long suspected but difficult to prove.

"Our initial plan was to look for drug resistance, not to prove that it was [a superinfection]," Jonathan Angel, MD, an infectious disease specialist at the University of Ottawa, tells WebMD. However, what Angel and his colleagues ultimately found could be the first documented case of an HIV superinfection. Luckily, a 1989 sample of the patient's blood was still in existence as a point of reference.

After determining that the person had begun a relationship with a man with advanced HIV in 1997, it was possible to compare genetic bits of the viruses in both individuals to see if they shared common elements. These genes were grown and analyzed as though the researchers were looking at different family trees. There were some striking similarities between the recent samples from the two men. However, the original 1989 sample was distinctly different.

"The genetic information suggests that there has been a transmission of one virus to the other," says Angel. On the one hand, he says, that's not surprising, because doctors assume HIV can re-infect a person in the early stages of the disease. What makes this case disturbing is that the apparent superinfection occurred years after the disease struck initially, when Angel says it's thought patients may have enough immune response to hold off another invasion from the virus.

"You could introduce a more virulent strain or a drug-resistant strain ... that was never there," says Angel. Thus, he says there is a public health message from the research. Namely, don't have sex with a previously infected person. Even if you have HIV, that's not a guarantee you couldn't get an even worse version of the disease that could wipe out the effectiveness of your current therapy. It's possible, says Angel, there could even be a "doomsday" strain that would be resistant to all therapy.

Though Angel has only discovered the likely superinfection once, he feels there is reason to act. "I think there's enough information here to raise awareness to say that this should be a public health issue whether we can prove it [to everyone's satisfaction]."

Infectious disease specialist Robert Schooley, MD, of the University of Colorado Health Sciences Center in Denver, tells WebMD that this looks like a genuine example of a superinfection. "The question that is more germane, I think, to patients is not whether this is a real case but how often it occurs." Schooley says the superinfection phenomenon is another example of the diversity of HIV, pointing to the difficulty of making an effective vaccine -- even for people who have some natural HIV immunity.

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