The global epidemiology of HIV/AIDS.

In this paper, the ways in which HIV is transmitted and factors facilitating transmission are described, although we still do not fully understand why the HIV epidemic has spread so heterogeneously across the globe. Estimates of HIV prevalence vary in quality but give some idea of trends in different countries and regions. Of all regions in the world, sub-Saharan Africa is the hardest hit by HIV, containing around 70% of people living with HIV/AIDS. There are, however, recent signs of hope in Africa due to a slight reduction in the number of new HIV cases in the year 2000. Most countries in Asia have not seen explosive epidemics in the general population up to now but patterns of injecting drug use (IDU) and sex work are conducive to the spread of HIV so there is no room for complacency. Unpredictable epidemics among IDU in the former Soviet Union have the potential to spread into the general population. Some countries in Central America and the Caribbean have growing HIV epidemics with adult prevalences second only to sub-Saharan Africa. Reductions in morbidity and mortality through the use of highly active antiretroviral therapy are at present limited to high-income and some Latin American countries. Both the cost of these therapies and the poor health care delivery systems in many affected countries need to be addressed before antiretrovirals can benefit the majority of people living with HIV/AIDS.