Human immunodeficiency virus (HIV) is categorized into two types, HIV-1 and HIV-2. Worldwide, most HIV infections are HIV-1, whereas HIV-2 largely has been confined to persons in or from West Africa. HIV-1 and HIV-2 have the same routes of transmission, and both can cause acquired immunodeficiency syndrome (AIDS); however, HIV-2 infections should be differentiated from HIV-1 infections because they are less likely to cause AIDS and their clinical management differs. CDC’s current surveillance case definition for HIV infection applies to both variants of HIV but lacks criteria for differentiating between HIV-1 and HIV-2.

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MMWR: HIV-2 Infection Surveillance — United States, 1987–2009