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EPIDEMIOLOGY

The human immunodeficiency virus (HIV) is the leading cause of infectious disease deaths worldwide. As of 2016, an estimated 36.7 million people worldwide and 1.2 million people in the United States1 have HIV infection or acquired immunodeficiency syndrome (AIDS). Although HIV exists everywhere across the globe, the vast majority of new infections (95%) occur in those living in low- and middle-income countries. In sub-Saharan Africa, the world’s most affected region, nearly 1 in every 20 adults is living with HIV.1

Despite the global burden, the number of new HIV infections and deaths is falling each year.2 Since the peak of the epidemic in 1996, new HIV infections dropped by nearly 50%; similar worldwide rates of AIDS-related deaths declined by more than 50% since the peak in 2004.3

Risks associated with acquiring HIV infection include homosexuality or bisexuality, injection drug use, heterosexual exposure, receipt of a blood transfusion prior to 1985, and maternal HIV infection (risk for vertical and horizontal maternal–neonatal transmission). Currently, the majority of HIV cases in the United States (67%) have occurred through men who have sex with men. Heterosexual contact accounts for approximately 24% of transmissions (with recent declines in that group), followed by about 6% associated with injection drug use and 3% with male-to-male sexual contact and IV drug use.4 New HIV infection rates continue to rise among young disadvantaged minority populations (many of whom use the ED for both primary and emergency care).

African Americans represent 12% of the total U.S. population but almost half (43%) of those with new HIV infections, the highest of any group by race and sex, notably in men having sex with men. Hispanics also have a higher proportion of new infections (26%) than accounted for by their relative size in the population (18%).5 ED visits by HIV-infected individuals occur at rates higher than the general population due to the characteristics of the populations who use the ED, which are the same groups disproportionately affected by HIV/AIDS.6

PATHOPHYSIOLOGY

HIV is a cytopathic retrovirus that kills infected cells. The virus is labile and neutralized easily by heat and common disinfecting agents such as 50% ethanol, 35% isopropyl alcohol, 0.3% hydrogen peroxide, or a 1:10 solution of household bleach. There are two major subtypes of HIV; HIV-1 is the predominant subtype worldwide and is the cause of AIDS. HIV-2 causes a similar immune syndrome, but exists primarily in western Africa and is infrequent in the United States, but its incidence is growing.

The HIV virion is a central RNA molecule and a reverse transcriptase protein surrounded by a core protein encased by a lipid bilayer envelope. After infection, HIV selectively attacks host cells involved in immune function, primarily CD4+ T cells. Within the host cell, HIV-encoded RNA uses reverse transcription to enter into DNA, aided by the enzyme ...

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