HIV infection can be passed from person to person in any of the following ways:
Unprotected sexual intercourse (heterosexual or homosexual anal, vaginal or oral sex) with an infected person
A contaminated transfusion (extremely rare in the United States since 1985, when blood products started being tested for HIV)
Needle sharing (if one intravenous drug user is infected)
Occupational exposure (needle stick with infected blood)
Artificial insemination with infected semen
Organ transplant taken from an HIV-infected donor
Newborns can catch HIV infection from their mothers before or during birth or through breastfeeding.
There is no evidence that HIV can be spread through the following: kissing; sharing food utensils, towels or bedding; swimming in pools; using toilet seats; using telephones; or having mosquito or other insect bites. Casual contact in the home, workplace or public spaces poses no risk of HIV transmission.
Although several HIV vaccines are being tested, none has been approved. You can decrease your chances of being infected with HIV by avoiding high-risk behaviors. To decrease the risk of HIV infection:
Have sex with only one partner who is also committed to having sex with only you. Consider getting tested together for HIV.
Use condoms with each act of sexual intercourse.
If you use intravenous drugs or inject steroids, never share needles.
If you are a health care worker, strictly follow universal precautions (the established infection-control procedures to avoid contact with bodily fluids).
If you are a woman thinking about becoming pregnant, have a test for HIV beforehand, especially if you or your partner have a history of behaviors that could have put you at risk of HIV infection. Pregnant women who are HIV-positive need special prenatal care and medications to decrease the risk that HIV will pass to their newborn babies.
If you believe you may have been exposed to HIV (through sexual contact or through exposure to blood, such as through a needle containing infected blood), medications may help prevent HIV infection before it takes hold in the body. The medication should be taken as soon as possible but not more than 72 hours (3 days) after exposure. If you think you may have been exposed, call your doctor or go directly for urgent care immediately.