The Facts
AIDS (acquired immune deficiency syndrome) was first recognized in North America in the early 1980s. It is caused by a virus named the human immunodeficiency virus (HIV). HIV infection has become a worldwide epidemic. About 33 million people are currently infected with the virus. In North America, the virus has infected nearly a million people and killed almost half a million people to date. At the end of 2006, about 1.1 million people in the United States had been living with HIV, and of these, an estimated 21% were unaware of their infection.
HIV is more common among certain populations at risk, such as people who inject illicit drugs, and bisexual and gay men. HIV infections are also increasing among women, Hispanics/Latinos, and African American communities.
Causes
The virus can be found in the blood, semen, vaginal fluid, and breast milk of infected people. HIV is also found in saliva, sweat, and tears, though not in high enough amounts to transmit the virus to another person. There are no known cases of anyone catching HIV through sneezing, shaking hands, or from toilet seats or mosquito bites.
The two most common ways to be infected with HIV in North America are through unprotected sex and sharing needles. HIV may be transmitted through unprotected heterosexual or homosexual, vaginal, anal, or oral sex. Although the risk of infection is lower with oral sex, it is still important to use protection during oral sex, such as a dental dam (a piece of latex to cover the vagina during oral sex) or a condom. HIV can also be passed on through perinatal infection, where mothers who have HIV are at risk of giving the disease to the baby during birth. The risk of perinatal infection is declining with new treatments. Breast-feeding by an infected mother can also transmit HIV.
Once HIV enters the bloodstream, it takes over cells vital to the immune response, known as CD4+ lymphocytes. The virus then inserts its own genes into the cell, turning it into a miniature factory that produces more copies of the virus. Slowly, the amount of virus in the blood goes up and the number of healthy CD4+ cells goes down. The destruction of CD4+ cells interferes with the body's ability to fight off infections and other diseases.
