HIV (human immunodeficiency virus) is a virus that attacks cells that help the body fight infection, causing increased vulnerability to other infections. Most commonly spread through unprotected sex and sharing injection drug equipment, HIV can lead to a diagnosis of AIDS (acquired immunodeficiency syndrome). An AIDS diagnosis is fatal; once diagnosed, people are typically given 3 years to live; however, HIV treatments are extremely effective and many never reach an AIDS diagnosis. HIV/AIDS was first identified in 1981 and remains a persistent, deadly epidemic.
Read more at HIV.gov