NAIROBI, Kenya—A quarter-century after AIDS was first identified, there is mounting evidence to suggest that the spread of HIV, the virus that causes AIDS, is at last slowing down.
The number of new HIV infections has fallen in most of sub-Saharan Africa and may be leveling off in India, regions that together account for more than three-quarters of the world's estimated 40.3 million HIV-infected people.
HIV isn't spreading in India and China as fast as experts feared just a few years ago. And in some regions, such as East Africa, there's evidence that people are having safer sex, slowing the spread of the virus and offering hope that AIDS prevention programs are working.
This doesn't mean that the AIDS crisis is over. The total number of people living with HIV continues to rise at an alarming rate, even if more slowly than before. The disease is overwhelming impoverished countries, and life-prolonging drugs remain out of reach for the vast majority of sufferers. In some countries, such as Mozambique, the spread of the virus continues to accelerate.
But many specialists now believe that in wide swaths of the world the explosion of new HIV infections is coming to an end, though they say it's still much too early to let down their guard.
"In all likelihood, new HIV infections have peaked globally," concluded a recent commentary in the British medical journal The Lancet. The commentary's authors were James D. Shelton and Daniel T. Halperin of the U.S. Agency for International Development and David Wilson of the World Bank.
Experts don't know precisely why HIV infection rates are slowing.
One reason suggested in The Lancet commentary is that conditions elsewhere in the world don't match those of southern Africa, where a epidemiological perfect storm made the region the center of the world's AIDS crisis.
The factors driving the region's "hyper-epidemic" included a large population of migrant workers and low levels of male circumcision, a procedure that experts now believe helps reduce HIV transmission. Sexual mores also played a major role: African men tend to have more long-term, concurrent sexual relationships than do men elsewhere, and they rarely use condoms in those relationships.
But the conditions are different in other regions of the world. In India, closely watched because its HIV-infected population of 5.2 million is by far the largest outside Africa, the virus has spread much more slowly than predicted, in part because Indian women appear to have fewer sex partners.
In China, officials recently revised the estimated number of total HIV infections downward—from 840,000 people to 650,000. The epidemic has stayed mostly confined to intravenous drug users and prostitutes, and United Nations projections from earlier in the decade that as many as 10 million people would be infected by 2010 now seem wildly overstated.
"There were very dramatic words a couple of years ago about India, about China, about what was coming—tremendously alarmist words," said Stephen Lewis, the U.N. secretary general's special envoy for HIV/AIDS in Africa.
"And it doesn't seem to have happened."
While mathematical models suggest that the spread of HIV is slowing, it's impossible to say for sure. AIDS symptoms don't show up for several years, so the newly HIV-infected often don't know they have HIV.
Most of the numbers for new infections are extrapolations, based on the results of HIV testing on limited portions of populations, such as pregnant women visiting prenatal clinics. From that data, researchers estimate what percentage of people ages 15 to 49 are infected with the virus, a figure that AIDS researchers call HIV prevalence. Annual changes in prevalence, in turn, are used to estimate the number of new infections in a given year.
Even if HIV has peaked, there's little cause to celebrate, researchers say.
For one, the rates of new infections in some countries remain horrendously high. Sub-Saharan Africa is likely to have at least 1 million to 2 million new infections each year for the next 10 to 20 years, said Dr. James Chin, a professor at the University of California-Berkeley and author of a forthcoming book on the AIDS pandemic.
For another, the slowdown may simply mean that in some countries most of the people likely to be infected—such as drug users and commercial sex workers—already are infected, so the pool of at-risk people has shrunk, according to The Lancet commentary. Efforts at prevention may have had little effect.
"Intrinsically it's a good thing—it means less new people are being infected," said Simon Gregson, a researcher at Imperial College in London who studies HIV in southern Africa. "But I'm not sure it represents a success."
Still, recent studies suggest that AIDS prevention programs are having an impact. AIDS researchers believe they're seeing fewer sexual partners and increases in condom use and other safe-sex practices in Uganda and Zimbabwe and in urban areas in Kenya and Haiti.
"The rapid explosion phase has passed in most of Africa," said John Stover, a senior fellow at the Futures Group, a public health consultancy. "So the challenge now is what to do to change sexual behaviors to bring (overall) prevalence down."
Despite its recent economic collapse, Zimbabwe is the first country in southern Africa where there's evidence that people are having safer sex. In surveys, fewer teenagers said they'd had sex before age 15, and both men and women reported having fewer sexual partners.
Researchers said that was partly responsible for drops in the rates of new infections. In recent studies in Zimbabwe's capital city, Harare, new infections among pregnant women fell from 4.8 percent in 1992 to 3.4 percent in 1999. Among factory workers they fell from 3 percent in 1994-95 to 1.3 percent in 2002-03.
In the rest of southern Africa, there's little evidence of behavior change. Rates of new infections have stabilized at very high levels. And worse, the infection rate in two countries, Botswana and Lesotho, seems to be ticking up again after a few years of decline.
Rates of new infection remain relatively low in West Africa, possibly, researchers say, because of the practice of male circumcision among many Muslim communities and local tribes.
In East Africa, a once-gloomy picture is brightening.
Kenya has reduced the number of new HIV infections among adults from 200,000 annually in the mid-1990s to about 80,000 now. Similar declines have been noted in neighboring Uganda.
In a 2003 survey, Kenyans reported having fewer sexual partners, and young people said they were waiting slightly longer to lose their virginity.
Earlier, success was limited to smaller epidemics such as Thailand and Cambodia, where the disease was concentrated in the sex industry.
Uganda and Kenya demonstrate that prevention efforts can work even when the disease is spreading among the general population, researchers say.
"East Africa continues to provide the most hopeful indications that serious AIDS epidemics can be reversed," the Joint U.N. Program on HIV/AIDS wrote in December.
In Central Asia and Eastern Europe, AIDS broke out among intravenous drug users in the post-Soviet upheaval of the 1990s, and HIV is now spreading to sex workers and their clients. But the general population remains relatively safe, and new infections have flattened out at about 270,000 per year.
Estimates of new infections in the United States have stabilized since 2000 at about 40,000 each year, according to the Centers for Disease Control and Prevention.
Europe follows the same trend. According to EuroHIV, the epidemiological monitoring center for 52 European nations, new cases reached a high of 113,930 in 2001 but had fallen to 71,755 by 2004, the last year for which complete numbers are available.
(Contributing to this report were Knight Ridder Newspapers correspondents Jack Chang in Rio de Janeiro, Tim Johnson in Beijing and Matthew Schofield in Berlin. Special correspondent Moritsugu reported from New Delhi. Bengali reported from Nairobi, Kenya.)
(c) 2006, Knight Ridder/Tribune Information Services.
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