HIV Highly Contagious Before Symptoms Show: Study

HIV may be highly transmissible before an infected person experiences its first, flu-like symptoms, and before HIV tests can detect the virus, researchers reported last week. The findings underscore the importance of consistent safe sex in preventing AIDS. The investigators studied five couples in whom HIV transmission occurred soon after one partner contracted the virus -- and as early as one week before the partner developed the flu-like symptoms that characterize early HIV infection.

"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 a statement from Dr. Christopher D. Pilcher of the University of North Carolina-Chapel Hill. Researchers had suspected but not documented this phenomenon, according to Pilcher. He and his colleagues reported their findings in the Oct. 10 issue of theJournal of the American Medical Association (2001; 286: 1713).

During the period shortly after transmission, known as primary HIV infection, virus levels soar in the blood, and short-lived symptoms such as fever, fatigue and swollen glands may occur. But because the immune system has not yet produced antibodies to the infection, standard tests for HIV antibodies cannot detect the infection. Researchers have theorized that during this period, large amounts of the virus are "shed" into the genital tract and make the patient highly infectious. The current study suggests that this is, indeed, the case.

The team came to its conclusions by taking the couples' sexual histories and genetically analyzing the HIV in their blood samples. All transmission had been suspected of occurring when one partner had a documented primary HIV infection. The researchers concluded that each case of a documented primary infection presents "a unique public health opportunity" to track down that person's recent sexual contacts and prevent the further spread of HIV.

"If you engage in unsafe sex, you cannot assume that you are not infected or infectious because you had a negative antibody test for HIV. The most commonly used tests can't show HIV for several weeks," Pilcher said.

Back to other CDC news for October 19, 2001

Previous Updates