How Is HIV Transmitted?
How Do You Get or Transmit HIV?
You can only get HIV by coming into direct contact with certain body fluids from a person with HIV who has a detectable viral load. These fluids are:
- Semen (cum) and pre-seminal fluid (pre-cum)
- Rectal fluids
- Vaginal fluids
- Breast milk
For transmission to occur, the HIV in these fluids must get into the bloodstream of an HIV-negative person through a mucous membrane (found in the rectum, vagina, mouth, or tip of the penis), through open cuts or sores, or by direct injection (from a needle or syringe).
People with HIV who take HIV medicine as prescribed and get and keep an undetectable viral load can live long and healthy lives and will not transmit HIV to their HIV-negative partners through sex.
How Is HIV Spread from Person to Person?
HIV can only be spread through specific activities. In the United States, the most common ways are:
- Having vaginal or anal sex with someone who has HIV without using a condom the right way every time or taking medicines to prevent or treat HIV. Anal sex is riskier than vaginal sex for HIV transmission. Learn more about the HIV risk associated with specific sexual activities.
- Sharing injection drug equipment, such as needles, syringes, or other drug injection equipment (“works”) with someone who has HIV because these items may have blood in them, and blood can carry HIV. People who inject hormones, silicone, or steroids can also get or transmit HIV by sharing needles, syringes, or other injection equipment. Learn more about HIV and injection drug use.
Less common ways are:
- An HIV-positive person transmitting HIV to their baby during pregnancy, birth, or breastfeeding. However, the use of HIV medicines and other strategies have helped lower the risk of perinatal transmission of HIV to less than 1% in the United States. Learn more.
- Being exposed to HIV through a needlestick or sharps injury. This is a risk mainly for health care workers. The risk is very low.
HIV is spread only in extremely rare cases by:
- Having oral sex. Oral sex carries little to no risk for getting or transmitting HIV. Theoretically, it is possible if an HIV-positive man ejaculates in his partner’s mouth during oral sex. Factors that may increase the risk of transmitting HIV through oral sex are oral ulcers, bleeding gums, genital sores, and the presence of other sexually transmitted diseases (STDs), which may or may not be visible. However, the risk is still extremely low, and much lower than with anal or vaginal sex.
- Receiving blood transfusions, blood products, or organ/tissue transplants that are contaminated with HIV. The risk is extremely small these days because of rigorous testing of the U.S. blood supply and donated organs and tissues. (And you can’t get HIV from donating blood. Blood collection procedures are highly regular and very safe.)
- Being bitten by a person with HIV. Each of the very small number of documented cases has involved severe trauma with extensive tissue damage and the presence of blood. This rare transmission can occur through contact between broken skin, wounds, or mucous membranes and blood or body fluids from a person who has HIV. There is no risk of transmission if the skin is not broken. There are no documented cases of HIV being transmitted through spitting as HIV is not transmitted through saliva.
- Deep, open-mouth kissing if both partners have sores or bleeding gums and blood from the HIV-positive partner gets into the bloodstream of the HIV-negative partner. HIV is not spread through saliva.
- Eating food that has been pre-chewed by a person with HIV. The only known cases are among infants. HIV transmission can occur when the blood from an HIV-positive caregiver’s mouth mixes with food while chewing and an infant eats it. However, you can’t get HIV by consuming food handled by someone with HIV.
Does HIV Viral Load Affect Getting or Transmitting HIV?
Yes. Viral load is the amount of HIV in the blood of someone who has HIV. If taken as prescribed, HIV medicine (called antiretroviral therapy or ART) can reduce a person’s HIV viral load very low level, which keeps the immune system working and prevents illness. This is called viral suppression, defined as having less than 200 copies of HIV per milliliter of blood.
HIV medicine can also make the viral load so low that a standard lab test can’t detect it. This is called having an undetectable level viral load. Almost everyone who takes HIV medicine as prescribed can achieve an undetectable viral load, usually within 6 months after starting treatment.
As noted above, people with HIV who take HIV medicine as prescribed and get and keep an undetectable viral load can live long and healthy lives and will not transmit HIV to their HIV-negative partners through sex.
HIV medicine is a powerful tool for preventing sexual transmission of HIV. But it works only if the HIV-positive partner gets and keeps an undetectable viral load. Not everyone taking HIV medicine has an undetectable viral load. To stay undetectable, people with HIV must take HIV medicine as prescribed and visit their health care provider regularly to get a viral load test. Learn more.
How is HIV Not Spread?
HIV is not spread by:
- Air or water
- Mosquitoes, ticks, or other insects
- Saliva, tears, sweat, feces, or urine that is not mixed with the blood of a person with HIV
- Shaking hands; hugging; sharing toilets; sharing dishes, silverware, or drinking glasses; or engaging in closed-mouth or “social” kissing with a person with HIV
- Drinking fountains
- Other sexual activities that don’t involve the exchange of body fluids (for example, touching).
- Donating blood
HIV can’t be passed through healthy, unbroken skin.
How Do You Get AIDS?
You can’t “catch” AIDS, which stands for acquired immunodeficiency syndrome.
AIDS is the most advanced stage of HIV infection. If a person has HIV and is not on HIV treatment, the virus will weaken the body’s immune system and the person will progress to AIDS.
People with AIDS have such badly damaged immune systems that they get a number of severe illnesses, called opportunistic infections.
However, thanks to today’s effective HIV treatment, most people with HIV in the U.S. do not have AIDS. People with HIV who take HIV medicine as prescribed and get and keep an undetectable viral load can stay healthy and will not progress to AIDS.
People who are HIV-negative can prevent getting HIV by using pre-exposure prophylaxis (PrEP), medicine that can stop HIV from taking hold in the body. There is also post-exposure prophylaxis (PEP), a short course of HIV medicines taken very soon after a possible exposure to HIV to prevent the virus from taking hold in your body. PEP must be started within 72-hours of a possible exposure to be effective. Learn more about these HIV prevention tools and other ways to prevent the sexual transmission of HIV.