AIDS Drugs Lower Infection Risk for Couples

Transmission less likely among heterosexuals when one partner takes medications, study shows

Randy Dotinga

Randy Dotinga

Published on May 13, 2005

FRIDAY, May 13, 2005 (HealthDay News) -- The new generation of AIDS drugs is doing more than helping HIV-positive people live healthier, longer lives: The medicines also greatly reduce the risk that infected heterosexuals will pass the virus along to their uninfected partners, new research suggests.

HIV-positive men and women were 80 percent less likely to infect their opposite-sex partners after the advent of powerful AIDS medications called antiretroviral therapy, according to Brazilian scientists.

The findings aren't unexpected, but they're definitely good news, said Dr. David Katzenstein, an AIDS specialist from Stanford University who's familiar with the study. Despite several attempts, researchers have had a hard time getting a handle on how AIDS drugs affect a person's ability to infect others, he said.

"This provides a great deal of support" for the theory that the drugs make people less infectious, he said. However, he cautioned that drug treatment doesn't eliminate the risk that an infected person will pass on the virus.

The findings appear in the May 12 online issue of the Journal of Acquired Immune Deficiency Syndromes.

The Brazilian researchers looked at the medical records of 393 heterosexual couples in which one person was HIV-positive and the other wasn't. The couples took part in the study if the HIV-negative partner took his or her first HIV test between 1991 and 2003.

Nearly 9 percent of the HIV-negative individuals whose partners didn't take antiretroviral therapy became HIV-positive. But none became infected if his or her partner took the drugs, which are designed to stop the AIDS virus from reproducing in the body, the study found.

The decline in transmissions held up even when the researchers adjusted their figures to account for factors such as frequency of unprotected sex.

The findings are similar to those of a Ugandan study that found HIV-positive people are less likely to infect their partners if the level of the virus in their blood is lower, Katzenstein said.

What should couples do if one person is HIV-positive?

Katzenstein said condoms remain the best defense against transmission of the disease. "As responsible medical professionals, we have to say there's always some risk from unprotected intercourse. The worst situation is doing nothing at all," he said.

And couples should remember that people appear to be most likely to transmit the virus when they don't even know they're infected. Some experts estimate that half of HIV transmissions happen because people have sex in the first weeks of infection, before they realize they're infected. During those weeks, the AIDS virus grows in the body before the immune system begins to fight back.

Since the infected person is unaware of the new infection, he or she doesn't take the drugs needed to keep the virus under control. At that time, Katzenstein said, uninfected partners appear to be at greatest risk.

More information

The U.S. Centers for Disease Control and Prevention offers more information about HIV and AIDS.

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