The extent of the epidemic

Population Reports, Sept, 1989 by Laurie Liskin, Cathleen A. Church, Phyllis T. Piotrow, John A. Harris

The Extent of the Epidemic At least through the turn of the century, acquired immune deficiency syndrome (AIDS) will kill more and more people each year. Perhaps half a million people now have AIDS or have already died of it (475). But far more--as many as 10 million--may be infected with the AIDS-causing human immunodeficiency virus (HIV) but have not yet developed AIDS (256). No one is known to have recovered from HIV infection. Thus, even if the spread of infection stopped today, more and more deaths would occur for years to come. But HIV infection has not stopped spreading. In most places infection rates are rising. In all, at least five million new AIDS cases are expected in the 1990s (478).

No one knows exactly how many people have developed AIDS. Between 1981, when AIDS was identified, and July 1989, about 170,000 cases were reported to the World Health Organization (WHO) by 149 countries (475). This is roughly one-third of the number thought to have actually occurred.

No one knows just how many people are infected with HIV, either. The prevalence of infection is estimated from blood tests performed on nonrandom samples of people in limited areas. Figures from these tests are difficult to extrapolate to entire countries.

Numbers of HIV infections and AIDS cases vary widely from one place to another. Prevalence and the characteristics of those infected depend on which of several modes of transmission dominates (see pp. 5-7). To date, 75 percent of cases reported worldwide have occurred in urban areas of North America and Western Europe (484). The rapidly rising prevalence of HIV infection in parts of Africa and Latin America, however, suggests that eventually the AIDS epidemic may hit these areas even harder.

North America and Europe

In North America and Western Europe HIV infection and AIDS cases have been concentrated among men who have sex with men and among users of intravenous drugs. In some US cities up to half of homosexual and bisexual men are infected (440) (see Table 1, p. 4). In the population as a whole, however, infection is uncommon--0.12 percent among US military recruits in 1988, for example (442).

The US accounts for 60 percent of the world's reported AIDS cases, with over 105,000 reported through mid-1989 (438). The US Centers for Disease Control estimate that as of 1988 between 1.0 and 1.5 million US residents were infected with HIV. About 50,000 new cases of AIDS are expected in 1989. By 1992 the annual number of new cases is expected to rise to 70,000, and the cumulative case load will top 365,000 (168).

Despite rapid growth in the number of AIDS cases in the US, the yearly rate of increase is slowing (168). This is largely the delayed result of safer sexual practices adopted among homosexual men. The percentage of AIDS cases involving homosexual men is decreasing and the percentage among intravenous drug users is increasing (484).

The distribution of AIDS cases in Western Europe and Canada resembles that in the US, but the numbers are smaller. As of September 1989 over 25,000 cases had been reported in Europe, and about 3,000 in Canada (496). France has the highest case load--over 7,100 cases, or more than 25 percent of the European total. The pattern of cases varies markedly in different European regions. In northern Europe infection is most common among homosexual men; in southern Europe, among intravenous drug users (256). Eastern Europe has reported few cases.

Africa

In many areas of sub-Saharan Africa the prevalence of HIV infection is high, and men and women are equally affected. An estimated two to three million Africans are infected with HIV, mostly in urban areas of Burundi, the Central African Republic, Cote d'Ivoire, Guinea-Bissau, Malawi, Rwanda, Tanzania, Uganda, Zaire, and Zambia. The national prevalence in these countries is estimated at about 2 to 4.5 percent of the entire population (477). Studies of selected populations in some cities of Central and East Africa have found prevalence as high as 30 percent, however (25, 216) (see Table 1).

About 25,000 AIDS cases had been reported in sub-Saharan Africa as of mid-1989, about 16 percent of the world's total. An estimated 90 percent of African AIDS cases are not reported, however (255).

In some African cities the prevalence of HIV infection is rising rapidly in groups such as pregnant women and blood donors that have not been considered at particularly high risk. Among populations at high risk--those who have many sexual partners, such as prostitutes and their clients--infection rates are rising even faster (see Table 1).

While infection rates in rural Africa are generally lower than those in cities, in some areas the epidemic has reached the countryside. For example, in 1983 HIV infection was virtually absent in the rural East Acholi district of northern Uganda. By 1986, 14 percent of health center outpatients and 13 percent of otherwise healthy people were infected (86).

HIV-2, a strain of HIV that is less widespread and perhaps less virulent than the first-identified AIDS virus, HIV-1, is common only in Western Africa. In Bissau, Guinea-Bissau, 4.7 percent of over 1,300 household members tested at randomly selected homes in 1987 were infected with HIV-2, while none was infected with HIV-1 (334).