AIDS Prevention Having an Effect
Sunday, August 3, 2008
Updated federal estimates of the annual number of new HIV infections in the United States, released yesterday, reveal that although the AIDS epidemic here is worse than previously thought, prevention efforts appear to be having some effect.
Even though the number of Americans living with HIV has risen by more than a quarter-million people since 1998 -- largely because of life-extending antiretroviral drugs -- the number of new cases each year has declined slightly over that period. That suggests that a person's likelihood of transmitting the virus to someone else is substantially lower now than it was a decade ago.
The new, if indirect, evidence that prevention programs are paying off was one of the few encouraging findings in an update on the American AIDS epidemic released yesterday by the Centers for Disease Control and Prevention on the eve of the 17th International AIDS Conference, in Mexico City.
"Over 95 percent of people living with HIV are not transmitting to someone else in a given year," said David R. Holtgrave, an expert on AIDS prevention at the Bloomberg School of Public Health at Johns Hopkins University. "What that says is the transmission rate has been kept very low by prevention efforts."
Those include targeting public health messages to high-risk groups, promoting widespread AIDS testing, and getting quick medical care for newly diagnosed cases, which in most cases lowers the person's infectiousness.
The CDC spends about $750 million a year on AIDS prevention. The main finding of its report is that HIV incidence in 2006 -- the latest year for which data are available -- was 56,300 new cases of infection. That is 40 percent higher than the previous government estimate of 40,000, but statistical back calculation suggests that HIV incidence has been unchanged since about 2000.
The more accurate estimate was possible for two reasons. A new testing method lets researchers detect infections that are less than six months old -- which is more quickly than before. New federal regulations also are pushing states to collect data on new HIV infections and not just new AIDS diagnoses.
By the time AIDS is diagnosed, the infection has severely damaged the immune system, making the person vulnerable to unusual infections and cancers. This generally occurs eight to 11 years after infection, assuming that there is no treatment with antiretroviral drugs, which can prolong life for many more years.
In December, The Washington Post reported that the CDC was revising HIV incidence upward to 50,000 to 60,000 cases a year. Yesterday's announcement -- and the publication of a paper in the Journal of the American Medical Association -- is the first official acknowledgment of the new, higher estimate.
"These data corroborate what many of us suspected -- that the epidemic is worse than we thought. However, it doesn't seem to be getting worse," said Jennifer Kates, director of HIV policy at the Kaiser Family Foundation in Washington.
The CDC's portrait of the American AIDS epidemic today shows that gay and bisexual men -- especially those who are young or black -- and their female partners are at particular risk.
In 2006, 73 percent of new HIV infections were in men, 53 percent were acquired through homosexual intercourse, and 45 percent were in African Americans. The incidence rate -- the number of infections per 100,000 people -- was seven times higher in blacks and three times higher in Hispanics than in whites. It was highest in people in their 30s, although people younger than 30 accounted for nearly 34 percent of new infections.