What are HIV and AIDS?

Because AIDS is caused by HIV, taking measures to avoid HIV infection can prevent AIDS.

Sexual exposures

Most HIV infections throughout the world are passed to other people through sex. This means that avoiding unprotected sex with infected persons can prevent most HIV infections. If both partners are uninfected, and both carefully avoid activities that might result in contracting HIV (both partners stay monogamous and do not share needles with others), unprotected sex can be safe.

If you do have sexual contact with a partner whose HIV status is uncertain, use latex or plastic condoms every time, from start to finish. For more information, see the "Additional resources" section at the end of this document, or call the US Centers for Disease Control and Prevention (CDC) at 1-800-232-4636 (1-800-CDC-INFO).

Injection drug use

The second most common cause of HIV infection is sharing used needles or drug equipment with injection drug users who have HIV. In some areas, public health and law enforcement policies are being developed to make sure that drug users can get clean needles and syringes. Nearly everywhere they have been started, these programs have reduced the number of new HIV infections in users who inject drugs.

For people who inject drugs, the safest way to avoid HIV is to quit. However, some people are unable to quit on their own or get help in quitting, and they may be unable to stop using drugs right away. For these people, clean needles and injection supplies can help protect them. This, in turn, helps to protect sex partners and any children they may have in the future. For more information on injection safety, see the "Additional resources" section at the end of this document, or call the CDC at 1-800-232-4636 (1-800-CDC-INFO).

After accidental exposure to HIV

In case of a broken condom or other accidental exposure from a person known to have HIV, some doctors offer "morning-after" treatment to try and reduce the risk of infection. If someone has an exposure from a person whose HIV status is not known, the person of unknown status can get a rapid HIV test to decide if the exposed person needs the treatment. This treatment consists of anti-HIV drugs, which must be taken every day for 4 weeks. They are likely to work best if they are started within 24 hours of the exposure and are rarely started more than 72 hours afterward. Because of the possible side effects and other limitations, this treatment is not advised for ongoing or frequent exposures. The drugs can cost $1,000 or more for the full treatment, and may not be covered by health insurance (see the "Anti-retroviral treatment" section). If this treatment is used, the exposed person gets HIV testing with follow-up medical visits.

Pregnancy and breast-feeding

HIV-infected mothers can pass the virus to their babies during pregnancy, delivery, or breast-feeding. Treating the mothers and infants with anti-HIV drugs and avoiding breast-feeding can greatly reduce the risk of these infections. Without this treatment, as many as 1 in 4 babies born to infected mothers can contract HIV. Women with HIV often do not know that they are infected because their only risky activity is sex with a man. That is why the US Public Health Service recommends that all women get tested for HIV early in their pregnancy, whether or not they have other known risk factors. This way, infections can be found in time to treat the mother and reduce the baby's HIV risk.

Women who are found to have HIV while they are pregnant are referred for treatment of their HIV to reduce the baby's risk, even if the woman doesn't need it for herself. The woman is offered anti-HIV drugs during the pregnancy and delivery. The infant is also treated for a few weeks after birth. Breast-feeding is avoided, if bottle feeding is safe and available. There may be other measures needed for the mother's health, some of which also may help reduce the baby's HIV risk. And in some cases, extra treatment is needed to further protect the infant. With expert care, the infant's risk of getting HIV from the mother can drop below 1 in 50. For more information, see "Additional resources" at the end of this document, or call the CDC at 1-800-232-4636 (1-800-CDC-INFO).

Receiving blood products and organ transplants

Transfusions of blood and blood products (such as factor VIII, given to people with hemophilia) caused some of the HIV infections in the early 1980s. With new precautions and careful testing at blood banks, this risk has been almost eliminated. Estimates place the risk of getting HIV this way at less than 1 out of every 2 million units of blood transfused.

Organ and tissue transplants from human donors may carry some risk of HIV and other infections. Donors are carefully screened and tested to reduce the risk as much as possible.

Summary of prevention measures

All told, the most effective methods to avoid HIV infection are:

• Not having sex
• Sex with only one uninfected partner, when both partners avoid other HIV risks
• Careful and correct condom use, every time, when partners' HIV risk is uncertain
• Not using injection drugs
• Always using sterile injection equipment if unable to stop using drugs
• To totally avoid the risk of passing HIV on to a baby, a woman with HIV may choose not to get pregnant.
• If a woman with HIV gets pregnant or wants to get pregnant, she should talk with an HIV expert as soon as possible. Together with her obstetrician, they can work to greatly reduce the baby's risk with anti-HIV drugs and other measures.