AIDS Infection Rate in U.S. Higher Than Previously Estimated
Saturday, August 2, 2008; 2:24 PM
Updated federal estimates of the annual number of new HIV infections in the United States, released today, reveal that while 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 the result 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 today 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 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. Today's announcement -- and the publication of a paper in the Journal of the American Medical Association -- is the first official acknowledgement 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.
The new study also sketches a 30-year picture of how the epidemic has evolved.
Annual incidence peaked in 1985 at 130,000 infections a year, dipped to 49,000 in the early 1990s, rose to 58,000 in 1998 and has now stabilized at about 56,000 a year.
The number of new of HIV cases acquired through drug injection fell by 80 percent over that period through reduced needle sharing by drug users and, in some places, needle-exchange programs. Infections acquired through homosexual sex, which also peaked in the early 1980s, fell to a low in the early 1990s but have risen steadily since then.
The epidemic in the black community is distinctly different from the national epidemic.
From 2001 to 2005, 38 percent of the new diagnoses in African Americans were in women, and 46 percent of new infections overall were from heterosexual contact. Among whites during the same period, 16 percent of new infections were in women, and 16 percent were from heterosexual transmission.
About half of the CDC's HIV prevention budget targets the black community, said Kevin Fenton, who heads those activities at the agency. He said, however, that the rising HIV incidence in gay men, and in young, black gay men especially, is evidence that prevention campaigns have "not reached all those who need it."
Statistics compiled by the Kaiser Family Foundation show that 4 percent of the $23 billion the U.S. government is spending this year on all HIV/AIDS activities (including research, medical care and overseas programs) goes toward prevention.
According to a paper published last year in the American Journal of Preventive Medicine, in inflation-adjusted dollars, the CDC's budget for AIDS prevention in 2006 was only 5 percent higher than it was in 1990.