HIV worldwide: What has happened? What has changed?

The human immunodeficiency virus (HIV) has resulted in a worldwide pandemic of infection. By 1991 more than 350,000 AIDS cases had been reported to the World Health Organization, but it is estimated that there are now more than 10 million people infected worldwide. HIV can rapidly spread in new populations: The pandemic is composed of multiple smaller epidemics. In the United States, it is estimated that over a million people are infected with HIV. Methods of estimating this number include extrapolation from the number of reported cases of AIDS, use of mathematical modeling and back-calculation, and seroprevalence surveys. Minorities continue to be overrepresented among those infected, and the prevalence of HIV in women is increasing. In serosurveys, it has been found that as HIV prevalence rates rise, the ratio of infected males to infected females approaches 1:1, suggesting an increased proportion of heterosexual transmission. HIV is now variably present but widespread across the United States. The epidemiology of HIV-related illnesses is also changing, as can be seen with current patterns of tuberculosis. HIV continues to be an increasingly complex and dangerous global burden.