Discussion Worldwide AIDS surveillance is coordinated by GPA at WHO in Geneva. Reports are received from collaborating centers, including CDC in the United States, the WHO Collaborating Centre in Paris, and WHO regional offices and ministries of health. Accuracy and completeness of AIDS reporting vary in different areas of the world. In Africa, reporting has only recently started in some countries and is, therefore, incomplete. Consequently, the proportion of AIDS cases that are reported in Africa is unknown.
Epidemiologic studies indicate three broad yet distinct geographic patterns of transmission.
I is typical of industrialized countries with large numbers of reported AIDS cases, such as North America, Western Europe, Australia, New Zealand, and parts of Latin America. In these areas, most cases occur among homosexual or bisexual males and urban IV drug users. Heterosexual transmission is responsible for only a small percentage of cases but is increasing. Pattern II is observed in areas of central, eastern, and southern Africa and in some Caribbean countries. IV drug use and homosexual transmission either do not occur or occur at a very low level.