The New York Times

Monday, January 31, 2000

Study Finds Low H.I.V. Levels May Restrict Spread of Virus

By THE ASSOCIATED PRESS

SAN FRANCISCO, Jan. 30 -- A study suggests that people with very low levels of H.I.V., the virus that causes AIDS, in their blood are unlikely to spread the virus to others.

The study was conducted in Africa but could have important implications in the United States, where drug treatment has lowered virus levels for many AIDS patients.

Health experts speculate that AIDS treatments may have an additional benefit -- slowing the epidemic by making infected people less likely to pass on the virus.

But the conditions studied in Africa do not precisely mirror the AIDS situation in the United States, and experts caution that the new research should not lull Americans into giving up safe-sex practices. Unprotected sex with a person infected by H.I.V. probably carries some risk, no matter how low the virus level.

The new study looked at sexual transmission of H.I.V. in rural Uganda. It was conducted by Dr. Thomas C. Quinn and others from Johns Hopkins University and presented today at the Seventh Conference on Retroviruses and Opportunistic Infections.

The doctors followed 415 heterosexual couples in which one partner was infected with H.I.V. and one was not. Despite receiving free condoms, the couples rarely used them. During 30 months of follow up, 90 people in the study caught the virus.

The study found that the higher the level of H.I.V. in the infected person's blood, the higher the risk of passing on the virus through sex.

Counting the number of individual viruses in a milliliter of blood, the study found that someone with 200,000 viruses per milliliter was two and a half times more likely to spread H.I.V. than someone with 2,000 viruses per milliliter.

But the researchers found no transmission of virus by infected people who carried less than 1,500 viruses per milliliter of blood, even if the people had sex without condoms.

Because of the high expense, AIDS treatment is rare in Africa.

In the United States, doctors typically try to reduce patients' virus levels to below the level of detection, about 50 viruses per milliliter. About half of all patients in the United States fail to reach this undetectable level consistently, but doctors say virus levels below 1,500 per milliliter of blood are common.

"It's wonderful news, and there is a lot we can learn from it," Dr. Helene Gayle, AIDS chief at the United States Centers for Disease Control and Prevention, said of the new study. But both she and Dr. Quinn cautioned that the situation in the United States was different from Africa, where, they noted, people may have low virus levels because their immune systems are strong enough to fight H.I.V. In the United States, virus levels are often lowered by treatment with AIDS medicines.

Doctors say it is theoretically possible that people with drug-suppressed H.I.V. carry more viruses than people with naturally low levels. If so, the risk of transmission could be greater.