Tim Brown: Tracking Asia's HIV/AIDS Epidemic

Date: 07-14-2004

***The information below was presented at the International AIDS Conference in Bangkok this week by Tim Brown, a senior research fellow at the East-West Center in Honolulu and a leading specialist on HIV/AIDS in Asia.

Asia Is Not Africa, But HIV Is No Less Serious

By Tim Brown, East-West Center

HIV epidemics in Asia follow a similar pattern, but vary in timing and severity. Most people are already familiar with this pattern. HIV epidemics in Asia begin in drug users who share needles and in homosexual and bisexual men. Then HIV starts to rise among sex workers and the men attending sexually transmitted disease clinics, who are largely the clients of sex workers. These men then transmit to their wives, who in turn pass HIV on to their children.

But we see variations in how quickly the epidemics grow and how serious they become around the region:

-- A few countries like Thailand, Cambodia, Myanmar and parts of India saw HIV epidemics take off rapidly in the late 1980s and very early 1990s. They have seen 1 to 3 percent of adults infected with HIV.

-- Other countries, e.g., China, Indonesia and Vietnam, have seen the epidemics start growing more gradually, but steadily, in the late 1990s. Most are at a few tenths to half a percent now.

-- A few countries, e.g., Bangladesh, Japan, Laos and the Philippines, have yet to see extensive HIV spread. Prevalence is below a tenth of a percent.

The East-West Center and its collaborators have developed a model based on this pattern that allows us to explore the factors controlling the speed and seriousness of HIV epidemics in Asia. We call this the "Asian Epidemic Model." The model allows us to vary the levels of risk behavior to fit specific countries and see the impact this has on the epidemic.

What the Asian Epidemic Model tells us:

-- Because many injecting drug users are clients of sex workers, HIV epidemics among them speed up the start of the epidemic between clients and sex workers. This means that delaying or preventing epidemics among injecting drug users can buy us valuable time to increase condom use between clients and sex workers.

-- The primary factor controlling the rate of growth and ultimate extent of HIV infection in a country is the size of the population of clients. In countries where 20 percent of adult men are clients of sex workers, e.g. Thailand and Cambodia, the epidemic grows rapidly and can reach high levels unless prevention programs achieve good coverage. In countries where only 5 percent of men are clients, the epidemics grow much more gradually, but they do eventually grow.

-- Most Asian epidemics developing now will grow gradually and steadily to reach levels of a few percent unless prevention programs are expanded. The recent epidemics in China, Indonesia and Vietnam, will most likely undergo steady growth until they reach several percent of the adult population. These are particularly dangerous, because the slow, steady growth is unlikely to raise alarm bells with policymakers.

-- Asian epidemics are and will stay focused in at-risk populations and their partners, making focused prevention extremely effective. The common picture that epidemics "break out" of at-risk populations and begin spreading widely in the general population is wrong. Women primarily have sex within marriage in Asia, and the levels of premarital and extramarital risk are low enough that less than 5 percent of new infections will occur this way. Most infections, even at advanced stages of the epidemics, will occur among clients and sex workers, injectors, males engaging in sex with other males and, a few years later, their wives. This means that focused prevention programs in Asia that concentrate prevention efforts on these populations can be extremely effective.

But that doesn't mean they'll remain small epidemics -- current responses are anemic and will allow continued epidemic growth. The clients of sex workers alone make up from 5 to 20 percent of adult males in most Asian countries. Their current or future wives add another 5 to 20 percent of the female population to those at higher risk of HIV. In countries where 10 percent of men are clients, the HIV infection level will probably stabilize somewhere around 3 to 5 percent without more effective prevention programs. They will never reach the levels of HIV infection seen in sub-Saharan Africa, but with Asia's large populations, each percentage point means large contributions to the global epidemic. And at present, the prevention coverage of the at-risk populations in most Asian countries is very poor, allowing HIV to continue spreading.

Tim Brown can be reached at tim@hawaii.edu

This is an East-West Wire, copyright East-West Center