October 2001

From University of North Carolina at Chapel Hill

Study: Infected people need not carry AIDS virus long before passing it on

CHAPEL HILL - People who contract HIV, the virus that causes AIDS, can pass that virus on to others within a week or two of picking it up themselves, a new study conducted at the University of North Carolina at Chapel Hill and in Switzerland shows.

Infectious people also can pass the virus on to others through a single sexual contact, the study found. In some cases, viral transmission occurs before the infected partner develops any temporary flu-like symptoms characteristic of early stages of the illness.

"The main thing that's new is that we've shown for the first time that sexual transmission can happen readily and very soon after exposure," said Dr. Christopher D. Pilcher, research assistant professor of medicine at the UNC School of Medicine. "Some doctors and scientists suspected that, of course, but no one had demonstrated it until now."

A report on the study appears in the current (Oct. 10) issue of the Journal of the American Medical Association. Besides Pilcher, authors include Dr. Joseph J. Eron Jr., associate professor of medicine at UNC, and six Swiss scientists in St. Gallen, Basel and Geneva.

"It has long been known that patients have very high levels of virus in the blood by the time the symptoms of acute HIV infection develop," Pilcher said. "Scientists have worried that there might be high levels of HIV shed into the genital tract during this time too, and their concern has led to the hypothesis that individuals with primary infection are highly infectious. This hypothesis would in part explain rapid spread of the epidemic and would suggest that this early stage of infection is an important target for intervention."

In fact, acute HIV infection is the earliest stage of infection, and routine tests for HIV antibodies are not yet positive. Patients often develop flu-like symptoms within one to four weeks of contracting it. Symptoms may last for several days and are sometimes called the "acute retroviral syndrome."

The research project involved studying in great detail five couples drawn from four university hospital clinics, he said. Clinicians took careful histories of sexual contacts and analyzed genetic material from HIV drawn from the patients to confirm that they got the virus from whom they thought they did. They also paid special attention to the early timing of infection.

"Our findings indicate that HIV is readily transmitted by sexual intercourse during early primary human infection and that the window of infectiousness then can begin as early as seven days before the onset of the acute retroviral syndrome," Pilcher said. "Each case of acute HIV infection may thus present a unique public health opportunity to abort rapid epidemic spread in sexual networks.

"Both source patients and secondary cases can be identified by urgently tracing recent sexual contacts, and secondary transmission risk can be reduced for all infected patients by counseling, along with anti-retroviral therapy or treatment for other sexually transmitted diseases."

Among other things, the new research underscores the importance of not engaging in unsafe sex, the physician said.

"If you engage in unsafe sex, you cannot assume that you are not infected or infectious just because you had a negative antibody test for HIV," he said. "The most commonly used tests can't show HIV for several weeks." The National Institutes of Health, the UNC General Clinical Research Center, the UNC and Duke Center for AIDS Research, the Swiss National AIDS Research Program, Bristol-Myers Squibb and Boehringer Ingelheim supported the research.

Note: Pilcher can be reached at 919-966-2536 or 216-3692 (pager).

By DAVID WILLIAMSON
UNC News Services












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