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The human immunodeficiency virus (HIV) and Acquired Immunodeficiency Syndrome (AIDS) remain a major cause of infectious disease deaths worldwide. Despite decades of diagnostic and therapeutic advances, increased life expectancies from highly active antriretrovirals are in general limited to high-income industrialized countries, and morbidity and mortality around the world remains high. The pandemic continues to significantly impact affect Sub-Saharan Africa, where heterosexual transmission is common and as many as 1 in 20 individuals live with HIV and AIDS. In the United States, there are approximately 50,000 new cases annually, with higher incidences in men who have sex with men and young minority populations.
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Human immunodeficiency virus is a cytopathic retrovirus that selectively attacks host cells involved in immune function, primarily CD4+ T cells. Infection ultimately results in persistent defects in cellular immunity which permit the development of opportunistic infections and neoplasms. Up to 90% of newly infected individuals have symptoms at the time of an acute HIV infection, most commonly nonspecific influenza-like symptoms that can go unrecognized. Symptoms usually develop 2 to 4 weeks after exposure, and can last for 2 to 10 weeks. The most common symptoms include fever (>90%), fatigue (70% to 90%), sore throat (>70%), rash (40% to 80%), headache (30% to 80%), and lymphadenopathy (40% to 70%).
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Seroconversion, which occurs when there is a detectable antibody response to HIV, usually occurs 3 to 8 weeks after infection, although delays of up to 11 months have been reported. This is followed by a long period of asymptomatic infection. The mean incubation time from exposure to the development of AIDS in untreated patients is 8 years in adults and 2 years in children under 5 years of age.
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Early symptomatic infection, when CD4 cell counts are 200 to 500 cells/mm3, is characterized by conditions that are more common and more severe in the presence of HIV infection but are not AIDS-defining conditions. Examples include thrush, persistent vulvovaginal candidiasis, peripheral neuropathy, cervical dysplasia, recurrent herpes zoster, and idiopathic thrombocytopenic purpura. As the CD4 count drops below 200 cells/mm3, the frequency of opportunistic infections increases. AIDS is defined by the appearance of any indicator condition (Table 92-1) or a CD4 count lower than 200 cells/mm3. Late symptomatic or advanced HIV infection exists in patients with a CD4 count lower than 50 cells/mm3 or clinical evidence of end-stage disease, including disseminated Mycobacterium avium complex (MAC) or disseminated Cytomegalovirus (CMV).
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