How HIV is Transmitted: Modes, Risks, and Prevention

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:

Blood
Semen (cum) and pre-seminal fluid (pre-cum)
Rectal fluids
Vaginal fluids
Breast milk

For transmission to occur, the HIV in these fluids must enter 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 achieve and maintain 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?

1. Sexual Contact : HIV is commonly transmitted through vaginal or anal sex with an infected person, particularly when a condom is not used correctly every time. Anal sex is considered riskier than vaginal sex for the transmission of HIV.

2. Sharing Injection Drug Equipment : HIV can be spread by sharing injection drug equipment, such as needles and syringes, with someone who has the virus. Blood in these items can carry HIV. This risk also applies to sharing needles for injecting hormones, silicone, or steroids.

3. Breast Milk : HIV can be transmitted from an HIV-positive mother to her baby through breast milk. This mode of transmission is a significant concern in regions where formula feeding is not feasible. However, with the use of antiretroviral therapy (ART) and other preventive measures, the risk of HIV transmission through breastfeeding can be significantly reduced.

Less common ways include:

1. Perinatal Transmission : HIV-positive individuals can transmit the virus to their baby during pregnancy, childbirth, or breastfeeding. However, the risk of perinatal transmission in the United States has been reduced to less than 1% due to the use of HIV medications and other preventive strategies.

2. Needlestick or Sharps Injury : Healthcare workers may be at risk of HIV exposure through needlestick or sharps injuries. However, the risk of transmission from such incidents 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 due to 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 regulated and very safe.)
Being bitten by a person with HIV. Each of the very few 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 to a very low level, which keeps the immune system working and prevents illness. This is called viral suppression, defined as having fewer 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 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 maintain 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. However, it works only if the HIV-positive partner achieves and maintains 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 healthcare 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)

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 progress to AIDS. People with HIV who take HIV medicine as prescribed and maintain an undetectable viral load can stay healthy and will not progress to AIDS.