Human immunodeficiency virus (hiv) infection

[Dianne]

Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and can cause acquired immunodeficiency syndrome (AIDS).

HIV is transmitted through close contact with a body fluid that contains the virus or cells infected with the virus (such as blood, semen, or vaginal fluids).
HIV destroys certain types of white blood cells, weakening the body’s defenses against infections and cancers.
When people are first infected, symptoms of fever, rashes, swollen lymph nodes, and fatigue may last a few days to several weeks.
Many infected people remain well for more than a decade.
About half of untreated people become ill and develop AIDS, defined by the presence of serious infections and cancers, within about 10 years.
Eventually, most untreated people develop AIDS.
Blood tests to check for HIV antibody and to measure the amount of HIV virus can confirm the diagnosis.
HIV drugs (antiretroviral drugs)—two, three, or more taken together—can stop HIV from reproducing, strengthen the immune system, and thus make people less susceptible to infection, but the drugs cannot eliminate HIV, which persists in an inactive form.

(See also HIV Infection in Children.)
HIV infections may be caused by one of two retroviruses, HIV-1 or HIV-2. HIV-1 causes most HIV infections worldwide, but HIV-2 causes many HIV infections in West Africa.
HIV progressively destroys certain types of white blood cells called CD4 lymphocytes. Lymphocytes help defend the body against foreign cells, infectious organisms, and cancer. Thus, when HIV destroys CD4 lymphocytes, people become susceptible to attack by many other infectious organisms. Many of the complications of HIV infection, including death, usually result from these other infections and not from HIV infection directly.
HIV-1 originated in Central Africa during the first half of the 20th century when a closely related chimpanzee virus first infected people. The global spread of HIV-1 began in the late 1970s, and AIDS was first recognized in 1981.
In 2016, about 36.7 million people, including 2.1 million children under age 15, were living with HIV infection worldwide. There were 1 million AIDS-related deaths, and 1.8 million people were newly infected.
Most (95%) new infections occur in the developing world. Almost 70% of new HIV infections occur in sub-Saharan Africa, with more than half occurring in women and 1 in 10 occurring in children under 15 years old. However, in many sub-Saharan African countries, the number of new HIV infections has greatly decreased, partly because of international efforts to provide treatment and strategies for prevention.
In the United States, over 1.1 million people aged 13 years or older were estimated to have HIV infection in 2015. About 15% of them do not know they have HIV infection. In 2016, 39,782 cases of HIV infection were diagnosed in the United States. Over two thirds of these infections occurred in gay and bisexual men. Among these men, most infections occurred in black men (10,223), followed by Hispanic/Latino men (7,425) and white men (7,390).