Through December of 1997, the United Nations AIDS Programme (UNAIDS) and the World Health Organization (WHO) estimate that over 30 million people are living with HIV infection worldwide, with the overwhelming majority living in developing countries and most not knowing that they are infected. Since 1981 and through November of 1997 more than 1.7 million cases of AIDS have been reported from 197 countries. More than 35% of these were reported from the United States, reflecting the relatively high incidence of the syndrome here and a well-established, national active surveillance system. All 50 states require that AIDS be reported to state health departments and subsequently without names to the Centers for Disease Control and Prevention (CDC).

The surveillance case definition for AIDS initially was developed before its cause was known, but was revised following the development of diagnostic tests for HIV infection and the widespread use of CD4 lymphocyte monitoring in clinical management of persons with HIV disease.

The current definition provides a consistent method to monitor trends of serious HIV-associated morbidity and mortality (Tables 409-1 and 409-2) . Patients infected with HIV exhibit a spectrum of manifestations ranging from no symptoms to AIDS. Systems have been developed to classify these manifestations in children and adults. Twenty-seven states also require reporting of all HIV infections. Because of the changing nature of the disease and due to the fact that currently available drugs may prevent the patient from developing an advanced immunodeficiency, there is a renewed interest in adding HIV infection to AIDS case reporting nationwide. However, different issues, such as confidentiality, have prevented this from being implemented uniformly throughout the United States.