Epidemiology of HIV-1 and HIV-2 infections in developing countries

The epidemiology and burden of HIV in the developing world are discussed earlier (see chapter 1). Two distinct viruses, HIV types 1 and 2 (HIV-1/HIV-2), cause AIDS. HIV-1 is responsible for the great majority of infections globally, HIV-2 being very rare outside of West Africa. Individual cases of HIV-2 infection have been described in other parts of Africa, Europe, the Americas, and Asia (India), but most people with HIV-2 infection have some epidemiological link to West Africa.

The routes of transmission of HIV-1 and HIV-2 (as described in chapter 1) are the same worldwide, but the relative importance of different modes of transmission differs according to region. In most developing countries, heterosexual transmission is the dominant mode of spread, and mother to child transmission of HIV is much more common than in industrialised countries. Homosexual transmission is rare in Africa, but is more common in South East Asia and central and south America. Transmission associated with injecting drug use is particularly frequent in parts of south and South East Asia and central and south America. Acquisition of infection from contaminated blood remains a problem, especially in parts of sub-Saharan Africa and south Asia; in some countries commercial blood donation acts to amplify the spread of transfusion-transmitted HIV infection, both to the recipients of blood as well as to donors who may become infected through exposure to unsterile equipment. Women and children are at especially high risk for transfusion transmitted HIV infection, the former because of the high incidence …