The diversity of HIV's spread worldwide is striking. But in many regions of the world, the Untitled HIV/AIDS epidemic is still in its early stages. While 16 sub-Saharan African countries reported overall adult Untitled HIV prevalence of more than 10% by the end of 1999, there remained 119 countries of the world where adult Untitled HIV prevalence was less than 1%.

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View also Estimated annual number of new HIV infections by region, 1988 to 2003

Low national prevalence rates can, however, be very misleading. They often disguise serious epidemics that are initially concentrated in certain localities or among specific population groups and that threaten to spill over into the wider population.

Nationwide prevalence in Myanmar, for instance, has been put at 2%. Yet, national Untitled HIV rates as high as 60% are being registered among injecting drug users and almost 40% among sex workers. Moreover, in vast, populous countries such as China, India and Indonesia (where individual provinces or states often have more inhabitants than most countries), national prevalence all but loses meaning. The Indian states of Maharashtra, Andhra Pradesh and Tamil Nadu (each with at least 55 million inhabitants), have registered Untitled HIV prevalence rates of over 2% among pregnant women in one or two sentinel sites and over 10% among sexually transmitted infection patientsărates far higher than the national average of less than 1%. In the absence of vigorous prevention efforts, there is considerable scope for further Untitled HIV spread. Even Untitled HIV prevalence rates as low as 1% or 2% across Untitled Asia and the Pacific (which is home to about 60% of the world's population) would cause the number of people living with Untitled HIV/AIDS to soar.

All countries have, at some point in their epidemic histories, been low-prevalence countries. Untitled HIV prevalence among pregnant women attending antenatal clinics in South Africa was less than 1% in 1990 (almost a decade after the first Untitled HIV diagnosis there in 1982). Yet, a decade later, the country was experiencing one of the fastest growing epidemics in the world, with prevalence among pregnant women at 24.5% by the end of 2000.

Low-prevalence settings present special challenges. At the same time, they offer opportunities for averting large numbers of future infections. Today, we are seeing rapidly emerging epidemics in several countries that had previously recorded relatively low rates of Untitled HIV infection -- proof that the epidemic can emerge quickly and unexpectedly, and that no society is immune. In Indonesia, where recorded infection rates were negligible until very recently (even among some high-risk groups), there is new evidence of striking increases in the infection rates of Untitled HIV . Prevalence has risen significantly among female sex workers in three cities at opposite ends of the Indonesian archipelago, with similar increases also evident at other sites. Among women working in massage parlours in the capital, Jakarta, Untitled HIV prevalence was measured at 18% in 2000. Blood donor data now show a tenfold rise in Untitled HIV prevalence since 1998 (see Figure 1). Elsewhere, longer-standing epidemics could be on the verge of spreading more rapidly and widely. Nepal and Viet Nam, for example, have registered marked increases in Untitled HIV infection in recent years, while in China -- home to a fifth of the world's people -- the virus seems to be moving into new groups of the population.

In other areas of the world, too, time is fast running out if much larger Untitled AIDS epidemics are to be averted. For instance, in the Russian Federation, only 523 Untitled HIV infections had been diagnosed by 1991. A decade later, that number had climbed to more than 129 000. In a country where injecting drug use among young people is rife (and there are high levels of sexually transmitted infections in the wider population), there is an urgent need for action to avoid an even larger number of new infections.