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Fact Sheet
Preventing Transmission of HIV
Part of HIV and Its Treatment

August 2012

Terms Used in This Fact Sheet

Sexually transmitted diseases (STDs): Infections that are usually passed during sex. HIV is an example of an STD.

Transmission of HIV: The spread of HIV from a person infected with HIV to another person through the infected person's blood, semen, genital fluids, or breast milk.

Tuberculosis (TB): A disease caused by germs that spread through the air when a person with active TB coughs, sneezes, or talks. TB usually affects the lungs.

Undetectable viral load: When the amount of HIV in a person's blood is too low to be detected with a viral load test.

Unprotected sex: Sex without using a condom.

Viral load: The amount of HIV in the blood. One of the goals of antiretroviral therapy is to reduce viral load.

How is HIV transmitted?

HIV is transmitted (spread) through the blood, semen, genital fluids, or breast milk of a person infected with HIV. The spread of the virus is called transmission of HIV.

Having unprotected sex or sharing drug injection equipment (such as needles and syringes) with a person infected with HIV are the most common ways HIV is transmitted.

Having a sexually transmitted disease (STD) can increase a person's risk of becoming infected with HIV during sex. The risk of spreading HIV during sex is also more likely if the partner infected with HIV also has another STD.

Women infected with HIV can transmit the virus to their babies during pregnancy or childbirth or by breastfeeding. If you are a woman infected with HIV, talk to your health care provider about ways to prevent pregnancy. If you are pregnant or plan to become pregnant, ask your health care provider how you can protect your baby from HIV. (See the HIV and Pregnancy fact sheets.)

I am taking anti-HIV medications and my viral load is undetectable. Can I still infect another person with HIV?

Your anti-HIV medications are doing a good job of controlling your infection. The amount of HIV in your blood is so low that a viral load test can't detect the virus. But having an undetectable viral load doesn't mean you're cured. You still have HIV. Although having an undetectable viral load greatly reduces the risk of HIV transmission, you can still infect another person with the virus.

How can I prevent transmitting HIV?


To prevent infecting another person with HIV:

Talk to your health care provider about how HIV is transmitted and ways to prevent spreading the virus. At each visit, discuss any high-risk behaviors (such as having unprotected sex or sharing drug injection equipment). Ask your health provider about testing for other STDs -- for you and your partner.

Talking about high-risk behaviors can be difficult. But it's important to be honest with your health care provider about any high-risk activities. Your health care provider can help you take steps to reduce your chances of transmitting HIV to another person.

Can I put my HIV-infected partner at risk?

Even if your partner is also infected with HIV, it's important to use condoms and not share drug injection equipement. You and your partner may have different strains of the virus. Your partner's HIV could act differently in your body or cause the anti-HIV medications you take to be less effective. And your strain of HIV could have the same effects on your partner.

Where can I find more information about HIV prevention?

The Centers for Disease Control and Prevention (CDC) National Prevention Information Network (NPIN) provides information about the prevention of HIV infection, other STDs, and tuberculosis (TB).

If you have questions about HIV transmission, call CDCINFO at 1-800-232-4636 or visit

For More Information

Contact an AIDSinfo health information specialist at 1-800-448-0440 or visit See your health care provider for medical advice.

This information is based on the U.S. Department of Health and Human Services' Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents.

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