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HIV Transmission

Image displaying various transmission categories for the HIV Basics: Transmission page—sex, IDU and mother-to-child transmission.

Myths persist about how HIV is transmitted. This section provides the facts about HIV risk from different types of sex, injection drug use, and other activities.

How is HIV passed from one person to another?

In the United States, HIV is spread mainly by having sex or sharing injection drug equipment such as needles with someone who has HIV.

Only certain fluids—blood, semen (cum), pre-seminal fluid (pre-cum), rectal fluids, vaginal fluids, and breast milk—from an HIV-infected person can transmit HIV. These fluids must come in contact with a mucous membrane or damaged tissue or be directly injected into the bloodstream (from a needle or syringe) for transmission to possibly occur. Mucous membranes can be found inside the rectum, the vagina, the opening of the penis, and the mouth.

In the United States, HIV is spread mainly by

Less commonly, HIV may be spread by

How well does HIV survive outside the body?

HIV does not survive long outside the human body (such as on surfaces), and it cannot reproduce. It is not spread by

Can I get HIV from anal sex?

Yes. In fact, having anal sex is the riskiest type of sex for getting or spreading HIV.

HIV can be found in the blood, semen (cum), preseminal fluid (pre-cum), or rectal fluid of a person infected with the virus. The bottom is at greater risk of getting HIV because the lining of the rectum is thin and may allow HIV to enter the body during anal sex, but the top is also at risk because HIV can enter through the opening of the penis or through small cuts, abrasions, or open sores on the penis. See the Prevention Q&As for more information.

Can I get HIV from vaginal sex?

Yes. In general vaginal sex is not as risky anal sex, but is still a high-risk behavior for HIV infection.

Yes. In general, vaginal sex is not as risky anal sex but is still a high-risk behavior for HIV infection. It is possible for either partner to become infected this way. This risk depends on many factors, including whether the partners are using condoms, whether the partner with HIV is using antiretroviral therapy (ART) consistently and correctly and whether the partner who is HIV-negative is using pre-exposure prophylaxis (PrEP) consistently and correctly. Condoms and HIV medicines can greatly lower the risk of transmitting HIV.

In women, HIV can be directly absorbed through the mucous membranes that line the vagina and cervix. The lining of the vagina can also sometimes tear and possibly allow HIV to enter the body.

In men, HIV can enter the body through the urethra (the opening at the tip of the penis) or through small cuts or open sores on the penis. Men who are not circumcised are at greater risk of HIV infection through vaginal sex than are circumcised men.

Risk for HIV infection increases if you or a partner also has a sexually transmitted disease (STD). See also Is there a connection between HIV and other sexually transmitted infections?

Many barrier methods that women use to prevent pregnancy (e.g., diaphragm, cervical cap) do not protect them against HIV or other STDs because they still allow infected semen (cum) to come in contact with the lining of the vagina.

Oral or hormonal contraceptives (e.g., birth control pills) do not protect women against HIV or other STDs.

Can I get HIV from oral sex?

Yes, but most types of oral sex carry little to no risk of HIV.

Oral sex involves giving or receiving oral stimulation to the penis (fellatio), the vagina (cunnilingus), or the anus (anilingus or rimming). Most types of oral sex carry little to no risk of HIV. The highest oral sex risk is performing oral sex (fellatio) with ejaculation in your mouth. However, the risk is still low, and much lower than anal or vaginal 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).

The risk is lower if the partners are using condoms or dental dams, if the partner with HIV is taking antiretroviral therapy (ART) consistently and correctly, and if the partner who is HIV-negative is taking pre-exposure prophylaxis (PrEP) consistently and correctly. Condoms and HIV medicines can greatly lower the risk of transmitting HIV.

For more information, see Oral Sex and HIV Risk.

Is there a connection between HIV and other sexually transmitted infections?

Yes. Having a sexually transmitted disease (STD) can increase the risk of getting or spreading HIV.

If you are HIV-negative but have an STD, you are at least 2 to 5 times as likely to get HIV if you have unprotected sex with someone who has HIV. There are two ways that having an STD can increase the likelihood of getting HIV. If the STD causes irritation of the skin (e.g., from syphilis, herpes, or human papillomavirus), breaks or sores may make it easier for HIV to enter the body during sexual contact. Even STDs that cause no breaks or open sores (e.g., chlamydia, gonorrhea, trichomoniasis) can increase your risk by causing inflammation that increases the number of cells that can serve as targets for HIV.

If you are HIV-positive and also infected with another STD, you are 3 to 5 times as likely as other HIV-infected people to spread HIV through sexual contact. This appears to happen because there is an increased concentration of HIV in the semen and genital fluids of HIV-positive people who also are infected with another STD.

CDC recommends sexually active gay and bisexual men test for:

Sometimes your health care provider may suggest a herpes test.

For more information about the connection between HIV and other STDs, see the CDC fact sheet, The Role of STD Detection and Treatment in HIV Prevention. To get tested for HIV or other STDs, find a testing site near you.

Can I get HIV from someone who is living with HIV but has undetectable viral load?

Yes. Even though having an undetectable viral load greatly lowers the chance that a person with HIV can transmit the virus to a partner, there is still some risk.

Viral load refers to the amount of HIV in the blood. An undetectable viral load is when the amount of HIV in the blood is so low that it can’t be measured. Antiretroviral therapy (ART) reduces viral load, ideally to an undetectable level, when taken consistently and correctly. A person with HIV can still potentially transmit HIV to a partner even if they have an undetectable viral load, because

Can I get HIV from injecting drugs?

Yes. If you share injection drug equipment with someone who has HIV, your risk is high.

Risk also depends on whether the person who has HIV is using antiretroviral therapy (ART) consistently and correctly, and whether the person who is HIV-negative is using preexposure prophylaxis (PrEP) consistently and correctly.

Sharing drug equipment (or works) can also be a risk for spreading HIV. Infected blood can get into drug solutions by

“Street sellers” of syringes may repackage used syringes and sell them as sterile syringes. For this reason, people who continue to inject drugs should get syringes from reliable sources of sterile syringes, such as pharmacies or needle-exchange programs.

It is important to know that sharing a needle or syringe for any use, including skin popping and injecting steroids, hormones, or silicone, can put you at risk for HIV and other blood-borne infections.

For more information, see If I use drugs, how can I prevent getting HIV?

Can I get HIV from using other kinds of drugs?

Not directly, but being drunk or high affects your ability to make safe choices and lowers your inhibitions, which may lead you to take risks such as having sex without a condom.

Methamphetamine (meth) is a very addictive stimulant that can be snorted, smoked, or injected. Even though using meth is an HIV risk factor for anyone who does it, there is a strong link between meth use and HIV transmission for men who have sex with men (MSM). MSM who use meth may increase their sexual and drug-use risk factors. They may

Drinking alcohol, particularly binge drinking, and using “club drugs” like Ecstasy, ketamine, GHB, and poppers can alter your judgment and impair your decisions about sex or other drug use. You may be more likely to have unplanned and unprotected sex or use other drugs, including injection drugs or meth. Those behaviors can increase your risk of exposure to HIV. If you have HIV, this can also increase your risk of spreading HIV to others.Treatment programs can help people stop using drugs or alcohol. Find a treatment facility near you or call 1-800-662-HELP (1-800-662-4357).

If I already have HIV, can I get another kind of HIV?

Yes. This is called HIV superinfection. The new strain of HIV can replace the original strain or remain along with the original strain. The effects of superinfection differ from person to person. For some people, superinfection may cause them to get sicker faster because they become infected with a new strain of the virus that is resistant to the medicines they are currently taking to treat their original HIV infection. Research suggests that the kind of superinfection where a person becomes infected with a new strain of HIV that is hard to treat is rare, less than 4%.

Are health care workers at risk of getting HIV on the job?

The risk of health care workers being exposed to HIV on the job (occupational exposure) is very low, especially if they use protective practices and personal protective equipment to prevent HIV and other blood-borne infections. For health care workers on the job, the main risk of HIV transmission is through accidental injuries from needles and other sharp instruments that may be contaminated with the virus; however, even this risk is small. Scientists estimate that the risk of HIV infection from being stuck with a needle used on an HIV-infected person is less than 1%.

For more information on preventing occupational exposure to HIV, see the CDC fact sheet, Occupational HIV Transmission and Prevention Among Health Care Workers.

Can I get HIV from receiving medical care?

Although HIV transmission is possible in health care settings, it is extremely rare.

Careful practice of infection control, including universal precautions (i.e., using protective practices and personal protective equipment to prevent HIV and other blood-borne infections) protects patients as well as health care providers from possible HIV transmission in medical and dental offices and hospitals.

The risk of getting HIV from receiving blood transfusions, blood products, or organ/tissue transplants that are contaminated with HIV is extremely small because of rigorous testing of the US blood supply and donated organs and tissues.

It is important to know that you cannot get HIV from donating blood. Blood collection procedures are highly regulated and safe.

For more information on preventing occupational exposure to HIV, see the CDC fact sheet, Occupational HIV Transmission and Prevention Among Health Care Workers. For more information on blood and tissue donations, see AIDS.gov’s Blood Transfusions and Organ Donation.

Can I get HIV from casual contact (“social kissing,” shaking hands, hugging, using a toilet, drinking from the same glass, or the sneezing and coughing of an infected person)?

No. HIV is not spread by day-to-day contact in the workplace, schools, or social settings. HIV is not spread through shaking hands, hugging, or a casual kiss. You cannot become infected from a toilet seat, a drinking fountain, a door knob, dishes, drinking glasses, food, cigarettes, pets, or insects.

HIV is not spread through the air, and it does not live long outside the body.

Can I get HIV from a tattoo or a body piercing?

Tattooing or body piercing present a potential risk of HIV transmission, but no cases of HIV transmission from these activities have been documented. Be sure that only new needles, ink, and other supplies are used and that the person doing the procedure is properly licensed.

Can I get HIV from being spit on or scratched by an HIV-infected person?

No. HIV cannot be spread through saliva, and there is no documented case of transmission from an HIV-infected person spitting on another person. There is no risk of transmission from scratching because there is no transfer of body fluids between people.

Can I get HIV from mosquitoes?

No. There is no evidence of HIV transmission from mosquitoes or any other insects—even in areas where there are many cases of HIV and large populations of mosquitoes. Unlike organisms that are transmitted by insect bites, HIV does not reproduce (and does not survive) in insects.

Can I get HIV from food?

Except for rare cases in which children consumed food that was pre-chewed by an HIV-infected caregiver, HIV has not been spread through food. The virus does not live long outside the body. You cannot get it from consuming food handled by an HIV-infected person; even if the food contained small amounts of HIV-infected blood or semen, exposure to the air, heat from cooking, and stomach acid would destroy the virus.

Are lesbians or other women who have sex with women at risk for HIV?

Case reports of female-to-female transmission of HIV are rare. The well-documented risk of female-to-male transmission shows that vaginal fluids and menstrual blood may contain the virus and that exposure to these fluids through mucous membranes (in the vagina or mouth) could, potentially, lead to HIV infection.

Is the risk of HIV different for different people?

Although HIV risk factors and routes of transmission apply to everyone equally, some people are at higher risk because of where they live and who their sex partners are.

The percentage of people living with HIV (prevalence) is higher in major metropolitan areas, so people who live there are more likely to encounter an HIV-positive person among their possible sex partners. (This atlas shows the prevalence of HIV for all US communities.) In the same way, because the prevalence of HIV is higher among gay and bisexual men and among black and Latino men and women, members of these groups are more likely to encounter partners who are living with HIV.

 
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