For the 33 million people around the world infected with HIV, the news seemed too good to be true and in many ways, it is. Researchers at the Swiss Federal Commission for HIV-AIDS issued a bold and provocative statement last week declaring that certain HIV-positive people receiving treatment for their infection are essentially "not sexually infectious, i.e. cannot transmit HIV through sexual contact."
The statement, published in the Bulletin of Swiss Medicine by respected and leading Swiss HIV experts, was certainly meant to pique and challenge both doctors and patients to rethink what it means to live with an HIV infection that is, for all intents and purposes, under control with antiretroviral medications (ARVs). It opens up the possibility that at least some people infected with HIV might be able to go without condoms and have unprotected sex. But experts warn that the challenge may only confuse patients about an already complex disease and the safest ways to both treat and contain it.
"On the one hand, I was struck that it was such as bold statement," says Rowena Johnston, vice president of research for the Foundation for AIDS Research (amfAR). "On the other hand, I would certainly have to be concerned about how this information is going to be used."
The World Health Organization (WHO) and the Centers for Disease Control (CDC) responded promptly by reaffirming their recommendation that all HIV positive people should use condoms during sexual activity to prevent the spread of the disease. "The issue that the Swiss article raises is an important thing to consider," says Dr. Robert Janssen, director of the division of HIV-AIDS Prevention at CDC. "But I think it's premature to make the type of recommendation that they are making."
As provocative as it is, the Swiss statement is actually based on some well-established scientific facts that AIDS researchers have accepted for some time now. Studies funded by the National Institutes of Health in Uganda, for example, showed that among heterosexual couples in which only one partner is HIV positive, the chances of spreading HIV are low if the HIV positive partner has low levels of virus circulating in the blood. Such viral load is also a key factor in determining whether HIV-positive pregnant women pass on the infection to their unborn children: women with lower viral loads have a smaller chance of infecting their babies. "The phenomenon of lower virus, less chance of transmission is well known," says Dr. Anthony Fauci, director of the NIH's National Institute of Allergy and Infectious Diseases. "The critical issue that gets people at the WHO, CDC and myself a little concerned is making the statement that there is essentially no risk of getting infected if you are having sex with a partner who is HIV-positive and on ARVs with virus below detectable levels. There is no such thing as zero risk."
In fact, viral-load tests are only rough guides for how much virus is circulating in an infected person's body; it's well known that HIV levels can blip upwards periodically. In addition, viral-load readings are generally done once every three months, so even if the virus is undetectable, which means there are fewer than 40 copies of HIV per ml of blood, there is no way of knowing what a person's viral count is at any given time. "There is no way of knowing what the viral count is for a person at home about to engage in a sexual encounter," says Johnston.
Fauci also notes that HIV tends to become compartmentalized in the body, which means that tests measuring HIV levels in the blood may not accurately reflect how much virus is sequestered in genital tissues and in fluid such as semen, particularly if the body is fighting off other infections with an inflammatory response.
Still, the statement raises the intriguing question of whether an HIV-positive person being treated successfully with ARVs can ever consider himself non-infectious. Johnston points out that if the assumption behind the Swiss statement is true, then it bodes well for efforts to control the epidemic worldwide. "We are now at the point where there are a couple million people in the developing world on ARVs, and we might at least be getting to the point where we can wonder if treating these people is actually going to reduce the spread of HIV as these people become somewhat less infectious." The important thing to remember, however, is that being less infectious is not the same as being non-infectious.