Acute human immunodeficiency virus type 1 (HIV-1) infection is a transient symptomatic illness associated with high-titer HIV-1 replication and a robust and expansive immunologic response to the invading pathogen. From 40 to 90 percent of new HIV-1 infections are associated with symptomatic illness. This syndrome is often undiagnosed or misdiagnosed, since HIV-1 antibodies are usually not detected during the early phase of infection. The diagnosis of acute HIV-1 infection requires a high index of clinical suspicion and correct use of specific diagnostic laboratory tests. Accurate early diagnosis is now particularly important because of the potential clinical benefit of early antiretroviral . . .