Study finds HIV infection can be highly contagious

January 06, 1995|By Knight-Ridder News Service

DETROIT -- Scientists have discovered another awful fact about AIDS: People are extremely contagious in the first 60 days after getting the AIDS virus -- the same period in which they can't possibly know they have it.

The practical implication of the findings: If you suspect your partner is having sex with others, you'd better use a condom. Tests can't detect the virus for four to six weeks -- when most of that risky, early phase has passed.

A University of Michigan study, being announced today by the university, found that in the first 60 days after being infected, a person could transmit the human immunodeficiency virus, which causes AIDS, to someone else in as many as a third of his sexual encounters.

After two months, HIV enters a long, less active phase, during which the chance of infecting someone else drops to three in 1,000 sexual encounters, says John Jacquez, senior author of the study published in the November Journal of Acquired Immune Deficiency Syndromes.

When the disease progresses to full AIDS status, a person's contagiousness rises again.

Earlier AIDS research, including a 1988 study by the Michigan team that prompted the current work, was unclear about how infectious this early phase is, Dr. Jacquez says.

"What we're saying is it's a lot higher than anyone thought," he says.

Some sexually active singles use AIDS testing as a way to reassure potential sexual partners that they are healthy. Yet, if they had acquired the virus recently enough, the test result may be wrong.

"This is the message for the person in the street: Don't rely on simple tests to measure if a person is contagious," says Dr. Carl Simon, professor of economics, public policy and mathematics at Michigan.

"The main impact of our work is that there is a very narrow time period of high contagiousness, less than two months, and that's before you can usually know you have HIV," Dr. Simon says.

The University of Michigan researchers believe the study raises other important public health questions. AIDS vaccine studies, for example, may want to include studies of contagiousness of vaccinated people who subsequently contract the infection.

Studies of a related virus in monkeys have shown that such a reduction of infectiousness is possible, Dr. Jacquez says.

The Michigan study is an analysis of several major studies in San Francisco and Chicago and computer simulations.

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