Sept. 13, 2000 -- The second wave of the U.S. AIDS epidemic may already have washed ashore. New York researchers report new infections with a type of HIV that has been linked to rapid heterosexual spread of the disease.
"Clinicians should be alert that a potentially more sexually transmissible virus has been brought to America, and thus could lead to a second wave of HIV infection in the U.S.," reports Mark H. Kaplan, MD, author of a study on the new strain. "The [strain of virus, dubbed] intersubtype recombinant HIV-1 A/E, which has been epidemic in Thailand and Africa, has arrived in the U.S."
Kaplan, an infectious disease specialist at North Shore University Hospital in Manhasset, N.Y., spoke at a meeting of the Institute of Human Virology in Baltimore. Some earlier studies have suggested that this strain of HIV, considered rare in the U.S., is associated with a higher rate of spread of the disease through heterosexual contact.
If true, the findings could have a major impact on how doctors manage the disease. Currently, HIV is managed by taking several different medications to fight it.
Kaplan and co-workers had reasoned that as New York City is one of the main points of entry for people entering the U.S., it might also be the port of entry for strains of HIV common in other countries. The researchers did sophisticated laboratory testing on virus samples obtained from the blood of 16 people with new HIV infections. The tests showed that 14 of the patients carried the subtype B virus, which is responsible for the vast majority of infections in the U.S. and western Europe. Two of the patients, though, were infected with a subtype of HIV more common in Africa -- A/E intersubtype recombinant.
The A/E virus arose in Africa among people infected with two different strains of HIV viruses, subtypes A and E. These viruses exchanged genetic material to create the A/E virus. When this virus got to Thailand, it spread explosively through the heterosexual population. The two New York infections reflect this background -- one patient became infected in Thailand, and the other was infected by her African husband.
There is no proof that that the A/E strain spreads more efficiently via sex than other types of the HIV virus. But several studies suggest that it may. For example, a Thai study presented at a 1994 international medical conference on AIDS found that the A/E type was more efficiently transmitted from an infected man to his uninfected wife than was the B subtype.
At the CDC, the person in charge of monitoring U.S. HIV subtypes is medical epidemiologist Hillard Weinstock, MD. He tells WebMD that Kaplan's report is the first he has heard of the A/E type of HIV in the U.S., and he urges caution in interpreting the findings.
"We don't think there is sufficient evidence at this point to say any ... non-B subtype is more transmissible or has a more virulent course," Weinstock says. "There has been speculation about that -- and some intriguing reports -- but I don't think the evidence is in yet."
Weinstock says the CDC's surveillance effort currently involves 10 U.S. cities, including New York. At another AIDS conference this year, his group reported that 1.7% of HIV infections in the U.S. are with subtypes of virus other than strain B.
The CDC is enrolling people in a new study to look at how common the unusual subtypes of HIV are, Weinstock says. "We haven't seen the data yet, but we would expect that, over time, the diversity of HIV would increase and in this country we would see more diverse subtypes," he says. He says he is not aware of any impact on current therapy yet, though the new findings do raise questions about HIV testing and vaccine development efforts.
For more information from WebMD, see our Diseases and Conditions page on HIV/AIDS.