Has The HIV Epidemic Rate Peaked?

The HIV epidemic appears to have stabilized around the world, according to "Has the HIV epidemic peaked?" published in the June issue of the Population Council's peer-reviewed journal Population and Development Review. The authors are Population Council Vice President and Distinguished Scholar John Bongaarts and three colleagues affiliated with the United Nations Population Division.

Although the rate of new infections has probably peaked in all world regions, the absolute number of HIV-positive individuals is expected to continue to grow in sub-Saharan Africa and remain near current levels worldwide--posing an ongoing challenge to public health programs. As a result of continued high rates of population growth and only moderate success of prevention programs in reducing HIV incidence, a large number of adolescents and adults are still likely to become infected.

Most of the world's 33.2 million HIV-positive individuals are likely to die of AIDS-related illnesses eventually. Further, with 2.5 million people being newly infected every year, the death toll from AIDS will remain high over the coming years.

The findings in "Has the HIV epidemic peaked?" also indicate that the percent of the population infected with HIV has stabilized everywhere in the world over the past decade except in Eastern Europe--where prevalence rates are expected to reach their highest point this year.

Worldwide approximately 0.8 percent of adults--ages 15-49--are infected with HIV. HIV prevalence is 1 percent or lower in all major world regions except in sub-Saharan Africa, where it is 5 percent. In this region, prevalence levels range from a fraction of 1 percent in several countries in Western Africa to above 15 percent in some Eastern and Southern Africa nations. The spread of infection among populations in this region has been more widespread because multiple and concurrent sexual partnerships are relatively common, male circumcision and condom use are relatively rare, and other sexually transmitted infections--which raise the risk of HIV transmission--are more prevalent.

Although trends vary, a general pattern in the past growth of the epidemic has been identified: a slow spread of the AIDS virus in the early 1980s or 1990s, followed by a period of rapid expansion, before reaching a relatively stable level. The appearance of plateaus implies that HIV is present in a small proportion of the population but that it does not generally spread beyond one or more subgroups.

The main explanation for this finding is that population subgroups have widely varying risks for infection. Sex workers and their clients, needle-sharing intravenous drug users, and men who have sex with men are the most vulnerable. Men and women living in monogamous unions or without sexual partners are at the opposite end of the spectrum. At first, the virus spreads quickly among the groups at highest risk, but then transmission slows when the individuals in those groups become infected or die, and the lower-risk groups remain uninfected. An epidemic reaches a plateau when the virus has achieved maximum penetration of the vulnerable groups. This point was reached in most countries by the early 2000s.

Declining prevalence rates in several countries are consistent with the view that current prevention efforts have had an impact. Despite these encouraging trends, high-risk behavior remains pervasive, and HIV continues to spread in much of the world.

"These findings indicate a continuing need to develop new prevention technologies and for prevention and treatment programs especially in the countries with substantial epidemics," Bongaarts concludes.

Bongaarts, John, Thomas Buettner, Gerhard Heilig, and Francois Pelletier. "Has the HIV epidemic peaked?" Population and Development Review 34(2): 199-224 (June 2008).