Natural history of HIV-1 and HIV-2 infections in developing countries
There is still relatively little information available about the natural history of HIV-1 and HIV-2 infections in the developing world. Prospective studies from industrialised countries before highly active antiretroviral therapy (HAART) was widely used suggest that after 10 years of infection with HIV-1, approximately 50% of people will have developed AIDS.
There has been a widespread belief that HIV-1 disease progresses more rapidly in developing countries, but more recent evidence suggests that the rate of progression from infection to severe immunosuppression may be little different from that documented in industrialised countries in the pre-HAART era.Because bacterial diseases such as pneumococcal disease and tuberculosis are prevalent in developing countries and may occur at relatively high CD4÷ lymphocyte (CD4) counts, some HIV-infected persons may appear to become symptomatic earlier. In addition, outcome may be worse in developing countries than in the industrialised world because of lack of access to care: this is almost certainly the main explanation for the reduced survival following the development of an AIDS- defining illness in developing countries, generally around six to nine months.
Progression from infection to disease is substantially slower for HIV-2 infection compared with HIV-1. Evidence for this includes individual reports of long survival with HIV-2 infection, higher levels of CD4 counts in HIV-2- than in HIV-1- infected people in cross-sectional studies, and a lower incidence of CD4 decline and AIDS in cohort studies comparing HIV-1- and HIV-2-infected people. Nonetheless, HIV-2 may eventually cause severe immunosuppression, accompanied by disease which is clinically indistinguishable from that caused by HIV-1.