Some experts predict that by 2010 Asia will have more HIV-infected people than the 30 million or so in sub-Saharan Africa. This, however, has got more to do with the size of the Asian population than an explosive spread of the virus. In fact, the Asian and African epidemics differ widely, and many epidemiologists say the disease is unlikely to become a 'generalised' epidemic in Asia as it has in Africa.
Jon Cohen describes the consensus and differences among experts regarding the trends — or lack of trends — that underlie the spread of AIDS in Asia. In Asia, the disease is characterised by 'local' epidemics concentrated in high-risk groups such as injecting drug users and sex workers. The speed at which it spreads by heterosexual sex is what will largely determine whether a more 'general' epidemic is likely. This in turn depends on behavioural patterns which, predictably, differ widely between African communities and Asian ones.
These debates affect aid workers as well, some of whom argue that localised epidemics are easier to combat than general ones. Other are concerned that the emphasis on the threat of a 'generalised' epidemic takes the focus off their primary concern of fighting the disease.
Reference: Science 304, 1932 (2004)