AIDS

Definition

Acquired immune deficiency syndrome (AIDS) is an infectious disease caused by the human immunodeficiency virus (HIV). AIDS is the advanced form of infection caused by HIV and typically only manifests itself after a long latency period after initial HIV infection. AIDS is a fatal disease for which there is currently no cure.

Description

First recognized in the United States in 1981, AIDS is considered one of the most devastating public health problems in recent history. The Centers for Disease Control and Prevention (CDC) has estimated that, as of June 2000, between 800,000 and 900,000 people in the United States were HIV-positive, and 312,000 were living with AIDS. Of adult AIDS cases, 47–53% were believed to have contracted HIV from same sex male intercourse, 25–31% from intravenous drug use, and 10% from heterosexual contact. There are an estimated 40,000 new HIV infections each year in the U.S. The Joint United Nations Program on HIV/AIDS estimates that, worldwide during the year 2000, an estimated 3 million people had died of AIDS, and 34.7 million adults and 1.4 million children were living with HIV/AIDS. Approximately 95% of persons with HIV/AIDS were living in developing countries.

Risk factors

HIV/AIDS can be transmitted in several ways. The various routes of transmission (and associated risk factors) include:

• Sexual contact. Persons at greatest risk are those who do not practice safe sex (sex with a condom), those who are not monogamous, those who engage in anal inter-course, and those who have sex with a partner with symptoms of advanced HIV infection and/or other sexually transmitted diseases (STDs). In the United States and Europe, most cases of sexually transmitted HIV infection arise via same sex contact, whereas in Africa the disease is spread primarily through heterosexual intercourse.
• Transmission in pregnancy. High-risk mothers include women who use intravenous drugs, women who have sex with bisexual men, women who are married to men who have an abnormal blood condition called hemophilia (a condition requiring blood transfusions), and women living in areas with a high rate of HIV infection among heterosexuals. The chances of transmitting HIV from mother to child are higher in women who are in advanced stages of the disease. Breast feeding increases the risk of transmission by 10%-20%, and vaginal delivery doubles the risk of transmitting HIV to the child. Zidovudine (AZT) given to the mother during pregnancy and given to the baby soon after delivery have been shown to decrease the risk of HIV transmission to the child.
• Exposure to contaminated blood or blood products. With the introduction of blood product screening in the mid-1980s, the incidence of HIV transmission in blood transfusions has dropped to 1 in 100,000. Among users of intravenous drugs, risk increases with the duration of injection use, the frequency of needle sharing, the number of persons who share a needle, and the number of AIDS cases in the local population.
• Exposure of health care professionals to infected blood. Studies have shown that 0.32% of highly exposed health care workers have become infected with HIV through occupational exposure. Needle injuries are the most common exposure route. Risk factors for contracting HIV from a needle injury include a deep injection, a needle that has been used in an artery or vein, blood visibly apparent on the needle prior to injury, and blood from a patient with end-stage AIDS. There is evidence that administration of zidovudine (AZT) to the injured worker soon after HIV exposure decreases risk of infection.

HIV is not transmitted by handshakes, coughing, sneezing, or other casual non-sexual contact. There is currently no evidence that HIV can be transmitted through bloodsucking insects such as mosquitoes.