SAN DIEGO — Frequent testing and drugs that suppress the virus that causes AIDS could potentially avert millions of cases of HIV-related tuberculosis, according to research presented February 20 at the annual meeting of the American Association for the Advancement of Science.
People whose immune systems are weakened by HIV are much more likely to get sick from infection with the TB bacterium, Mycobacterium tuberculosis. Worldwide, TB kills as many as half of all people with AIDS, according to the Joint United Nations Programme on HIV/AIDS.
To explore the best ways to slow the spread of HIV and TB, a team led by Brian Williams of the South African Centre for Epidemiological Modelling and Analysis in Stellenbosch created a mathematical model of disease spread under different treatment strategies in sub-Saharan Africa using previously published data. For the nine countries considered, the model suggests, yearly HIV testing and immediate treatment with antiretroviral therapy would avert more than 6 million cases of TB by the year 2050.
These numbers go down if treatment is delayed after infection, which means people infected with HIV should begin antiretroviral therapy even when their immune function has not yet seriously declined, Williams notes in an unpublished paper.
In southern Africa, an estimated 73 percent of new TB patients are coinfected with HIV. While antiretroviral therapy is expensive, the costs are dwarfed by the costs of doing nothing, Williams said. “We’re losing our young adults at a time when they should be contributing to society,” he said.
A vaccine against tuberculosis designed specifically for people coinfected with HIV may be available in the not-too-distant future. A clinical trial of about 2,000 people in Tanzania found that the vaccine seemed effective against TB without adverse effects on immune function, researchers reported online January 28 in the journal AIDS.
Regular testing for HIV is crucial for effective treatment even if a person is not infected with TB, researchers at the conference session noted. In the United States, between 20 and 25 percent of people infected with HIV don’t know that they have it, said Kenneth Mayer of BrownUniversity in Providence, Rhode Island.