Group O human immunodeficiency virus-1 infections.

Human immunodeficiency viruses (HIV), the cause of AIDS, have remarkable genetic diversity. Among the HIV-1 viruses are the "major" (group M) HIV-1 subtypes and genetic "outliers" that have been designated as group O viruses. Group O viruses are most prevalent in parts of Africa, although they have also been reported in Europe and the United States and are associated with AIDS. Because group O viruses are so highly divergent, tests designed to detect group M viruses may be unreliable in the diagnosis of group O infection. Modification of these tests are needed to protect the safety of the blood supply.