HIV Transmission and Prevention

HIV is a blood-borne virus that is transmitted through infected blood, semen, vaginal secretions, and breast milk. To enter the body, the virus must come into direct contact with the bloodstream, with a mucous membrane, or with broken skin. HIV is most often transmitted through sexual contact and shared needles.

Anal and vaginal intercourse are known to efficiently transmit HIV. Oral sex on a man has a much lower transmission rate. Other types of sexual activity such as oral sex on a woman or manual contact with the genitals are very unlikely to transmit the virus. The presence of other sexually transmitted infections such as syphilis, gonorrhea, or genital herpes increases the risk of sexual transmission of HIV. HIV-infected people with no symptoms can still transmit the virus.

Many people have contracted HIV through sharing needles, syringes, and other “works” to inject drugs. Needles used for tattooing and body piercing are also a possible transmission route. Health-care workers may contract HIV through needle-sticks or other accidental exposures on the job. Many people contracted HIV through blood transfusions before the HIV antibody test was developed in 1985; today donated blood is tested and heat-treated and is considered safe.

HIV can also be transmitted from mother to child during pregnancy or birth (vertical or perinatal transmission) or through breast-feeding. Vertical transmission is more likely if the mother has a high viral load. Use of antiretroviral drugs such as AZT or nevirpine can reduce the risk of vertical transmission from about 25% to about 5% or less. In the U.S. and other developed countries it is recommended that women with HIV should not breast-feed their babies.

There is no evidence that HIV is transmitted through saliva, sweat, tears, or urine, and the virus cannot live long outside the human body. HIV is not transmitted through casual or household contact including hugging or kissing, coughing or sneezing, or sharing eating utensils or drinking glasses.

There is currently no vaccine to prevent HIV, although much research in this area is underway. If a person has been exposed to HIV, they may be eligible for post-exposure prophylaxis (PEP). PEP involves starting anti-HIV drugs within 72 hours of exposure. It is not known whether PEP can help prevent or reduce the severity of HIV disease in people exposed through sex or needle sharing, but it has shown benefits in health-care workers accidentally exposed on the job.

 
HIV Prevention Guidelines

• Do not share needles or other equipment to inject drugs; obtain new needles from a needle exchangeor—if you must share— clean needles and syringes thoroughly with bleach.

• Practice safer sex, including the consistent use of latex condoms and barriers with water-based lubricants; avoid products that contain nonoxynol-9.

• Tattooists, piercers, and acupuncturists should use new needles for each client.

• Do not share personal items such as toothbrushes.

• Exercise universal precautions in health-care settings, including use of latex gloves.

• Properly dispose of used needles, bandages, and menstrual supplies; clean and disinfect spilled body fluids.