HIV Transmission

• How is HIV passed from one person to another?
• Which body fluids transmit HIV?
• How well does HIV survive outside the body?
• Can I get HIV from kissing?
• Can I get HIV from oral sex?
• Can I get HIV from anal sex?
• Can I get HIV from vaginal sex?
• Is there a connection between HIV and other sexually transmitted diseases?
• Why is injecting drugs a risk for HIV?
• Are health care workers at risk of getting HIV on the job?
• Are patients in a health care setting at risk of getting HIV?
• Are "lesbians" or other women who have sex with women at risk for HIV?
• Can I get HIV from getting a tattoo or through body piercing?
• Can I get HIV from a bite?
• Can I get HIV from casual contact (shaking hands, hugging, using a toilet, drinking from the same glass, or the sneezing and coughing of an infected person)?
• Can I get HIV from mosquitoes?
• Can I get HIV while playing sports?

How is HIV passed from one person to another?

HIV transmission can occur when blood, semen (cum), pre-seminal fluid (pre-cum), vaginal fluid, or breast milk from an infected person enters the body of an uninfected person.

HIV can enter the body through a vein (e.g., injection drug use), the lining of the anus or rectum, the lining of the vagina and/or cervix, the opening to the penis, the mouth, other mucous membranes (e.g., eyes or inside of the nose), or cuts and sores. Intact, healthy skin is an excellent barrier against HIV and other viruses and bacteria.

These are the most common ways that HIV is transmitted from one person to another:

• by having sex (anal, vaginal, or oral) with an HIV-infected person;
• by sharing needles or injection equipment with an injection drug user who is infected with HIV; or
• from HIV-infected women to their babies before or during birth, or through breast-feeding after birth.

HIV also can be transmitted through receipt of infected blood or blood clotting factors. However, since 1985, all donated blood in the United States has been tested for HIV. Therefore, the risk of infection through transfusion of blood or blood products is extremely low. The U.S. blood supply is considered to be among the safest in the world.

For more information, see "How safe is the blood supply in the United States?"

Some health-care workers have become infected after being stuck with needles containing HIV-infected blood or, less frequently when infected blood comes in contact with a worker's open cut or is splashed into a worker's eyes or inside their nose. There has been only one instance of patients being infected by an HIV-infected dentist to his patients.

For more information, see "Are health care workers at risk of getting HIV on the job?" and "Are patients in a health care setting at risk of getting HIV?" If you would like more information or have personal concerns, call CDC-INFO 24 Hours/Day at 1-800-CDC-INFO (232-4636), 1-888-232-6348 (TTY), in English, en Español.

Which body fluids transmit HIV?

These body fluids have been shown to contain high concentrations of HIV:

• blood
• semen
• vaginal fluid
• breast milk
• other body fluids containing blood

The following are additional body fluids that may transmit the virus that health care workers may come into contact with:

• fluid surrounding the brain and the spinal cord
• fluid surrounding bone joints
• fluid surrounding an unborn baby

HIV has been found in the saliva and tears of some persons living with HIV, but in very low quantities. It is important to understand that finding a small amount of HIV in a body fluid does not necessarily mean that HIV can be transmitted by that body fluid. HIV has not been recovered from the sweat of HIV-infected persons. Contact with saliva, tears, or sweat has never been shown to result in transmission of HIV.

How well does HIV survive outside the body?

Scientists and medical authorities agree that HIV does not survive well outside the body, making the possibility of environmental transmission remote. HIV is found in varying concentrations or amounts in blood, semen, vaginal fluid, breast milk, saliva, and tears. To obtain data on the survival of HIV, laboratory studies have required the use of artificially high concentrations of laboratory-grown virus. Although these unnatural concentrations of HIV can be kept alive for days or even weeks under precisely controlled and limited laboratory conditions, CDC studies have shown that drying of even these high concentrations of HIV reduces the amount of infectious virus by 90 to 99 percent within several hours. Since the HIV concentrations used in laboratory studies are much higher than those actually found in blood or other specimens, drying of HIV-infected human blood or other body fluids reduces the theoretical risk of environmental transmission to that which has been observed - essentially zero. Incorrect interpretations of conclusions drawn from laboratory studies have in some instances caused unnecessary alarm.

Results from laboratory studies should not be used to assess specific personal risk of infection because (1) the amount of virus studied is not found in human specimens or elsewhere in nature, and (2) no one has been identified as infected with HIV due to contact with an environmental surface. Additionally, HIV is unable to reproduce outside its living host (unlike many bacteria or fungi, which may do so under suitable conditions), except under laboratory conditions; therefore, it does not spread or maintain infectiousness outside its host.

Can I get HIV from kissing?

On the Cheek:

HIV is not transmitted casually, so kissing on the cheek is very safe. Even if the other person has the virus, your unbroken skin is a good barrier. No one has become infected from such ordinary social contact as dry kisses, hugs, and handshakes.

Open-Mouth Kissing:

Open-mouth kissing is considered a very low-risk activity for the transmission of HIV. However, prolonged open-mouth kissing could damage the mouth or lips and allow HIV to pass from an infected person to a partner and then enter the body through cuts or sores in the mouth. Because of this possible risk, the CDC recommends against open-mouth kissing with an infected partner.

One case suggests that a woman became infected with HIV from her sex partner through exposure to contaminated blood during open-mouth kissing.

For more information refer to the July 11, 1997, Morbidity and Mortality Weekly Report "Transmission of HIV Possibly Associated with Exposure of Mucous Membrane to Contaminated Blood" located at www.cdc.gov/mmwr/preview/mmwrhtml/00048364.htm.

Can I get HIV from oral sex?

Yes, it is possible for either partner to become infected with HIV through performing or receiving oral sex. There have been a few cases of HIV transmission from performing oral sex on a person infected with HIV. While no one knows exactly what the degree of risk is, evidence suggests that the risk is less than that of unprotected anal or vaginal sex.

If the person performing oral sex has HIV, blood from their mouth may enter the body of the person receiving oral sex through

• the lining of the urethra (the opening at the tip of the penis);
• the lining of the vagina or cervix;
• the lining of the anus; or
• directly into the body through small cuts or open sores.

If the person receiving oral sex has HIV, their blood, semen (cum), pre-seminal fluid (pre-cum), or vaginal fluid may contain the virus. Cells lining the mouth of the person performing oral sex may allow HIV to enter their body.

The risk of HIV transmission increases

• if the person performing oral sex has cuts or sores around or in their mouth or throat;
• if the person receiving oral sex ejaculates in the mouth of the person performing oral sex; or
• if the person receiving oral sex has another sexually transmitted disease (STD).

Not having (abstaining from) sex is the most effective way to avoid HIV.

If you choose to perform oral sex, and your partner is male,

• use a latex condom on the penis; or
• if you or your partner is allergic to latex, plastic (polyurethane) condoms can be used.

Studies have shown that latex condoms are very effective, though not perfect, in preventing HIV transmission when used correctly and consistently. If either partner is allergic to latex, plastic (polyurethane) condoms for either the male or female can be used. For more information about latex condoms, see "Male Latex Condoms and Sexually Transmitted Diseases" (PDF).

If you choose to have oral sex, and your partner is female,

• use a latex barrier (such as a natural rubber latex sheet, a dental dam or a cut-open condom that makes a square) between your mouth and the vagina. A latex barrier such as a dental dam reduces the risk of blood or vaginal fluids entering your mouth. Plastic food wrap also can be used as a barrier.

If you choose to perform oral sex with either a male or female partner and this sex includes oral contact with your partners anus (analingus or rimming),

• use a latex barrier (such as a natural rubber latex sheet, a dental dam or a cut-open condom that makes a square) between your mouth and the anus. Plastic food wrap also can be used as a barrier.

If you choose to share sex toys with your partner, such as dildos or vibrators,

• each partner should use a new condom on the sex toy; and
• be sure to clean sex toys between each use.

If you would like more information or have personal concerns, call CDC-INFO 24 Hours/Day at 1-800-CDC-INFO (232-4636), 1-888-232-6348 (TTY), in English, en Español.

Can I get HIV from anal sex?

Yes. In fact, unprotected (without a condom) anal sex (intercourse) is considered to be very risky behavior. It is possible for either sex partner to become infected with HIV during anal sex. HIV can be found in the blood, semen, pre-seminal fluid, or vaginal fluid of a person infected with the virus. In general, the person receiving the semen is at greater risk of getting HIV because the lining of the rectum is thin and may allow the virus to enter the body during anal sex. However, a person who inserts his penis into an infected partner also is at risk because HIV can enter through the urethra (the opening at the tip of the penis) or through small cuts, abrasions, or open sores on the penis.

Not having (abstaining from) sex is the most effective way to avoid HIV. If people choose to have anal sex, they should use a latex condom. Most of the time, condoms work well. However, condoms are more likely to break during anal sex than during vaginal sex. Thus, even with a condom, anal sex can be risky. A person should use generous amounts of water-based lubricant in addition to the condom to reduce the chances of the condom breaking.

For more information on latex condoms, see "Male Latex Condoms and Sexually Transmitted Diseases" (PDF).

If you would like more information or have personal concerns, call CDC-INFO 24 Hours/Day at 1-800-CDC-INFO (232-4636), 1-888-232-6348 (TTY), in English, en Español.

Can I get HIV from vaginal sex*?

Yes, it is possible for either partner to become infected with HIV through vaginal sex* (intercourse). In fact, it is the most common way the virus is transmitted in much of the world. HIV can be found in the blood, semen (cum), pre-seminal fluid (pre-cum) or vaginal fluid of a person infected with the virus.

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

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.

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

Not having (abstaining from) sex is the most effective way to avoid HIV. If you choose to have vaginal sex, use a latex condom to help protect both you and your partner from HIV and other STDs. Studies have shown that latex condoms are very effective, though not perfect, in preventing HIV transmission when used correctly and consistently. If either partner is allergic to latex, plastic (polyurethane) condoms for either the male or female can be used.

For more information on latex condoms, see "Male Latex Condoms and Sexually Transmitted Diseases" (PDF).

If you have additional questions or are concerned about personal behaviors, call CDC-INFO 24 Hours/Day at 1-800-CDC-INFO (232-4636), 1-888-232-6348 (TTY), in English, en Español.

* For the purpose of this FAQ, vaginal sex or intercourse refers to sexual activity between a man and a woman involving the insertion of the penis into the vagina.

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

Yes. Having a sexually transmitted disease (STD) can increase a person's risk of becoming infected with HIV, whether the STD causes open sores or breaks in the skin (e.g., syphilis, herpes, chancroid) or does not cause breaks in the skin (e.g., chlamydia, gonorrhea).

If the STD infection causes irritation of the skin, breaks or sores may make it easier for HIV to enter the body during sexual contact. Even when the STD causes no breaks or open sores, the infection can stimulate an immune response in the genital area that can make HIV transmission more likely.

In addition, if an HIV-infected person is also infected with another STD, that person is three to five times more likely than other HIV-infected persons to transmit HIV through sexual contact.

Not having (abstaining from) sexual intercourse is the most effective way to avoid all STDs, including HIV. For those who choose to be sexually active, the following HIV prevention activities are highly effective:

• Engaging in behaviors that do not involve vaginal or anal intercourse or oral sex
• Having sex with only one uninfected partner
• Using latex condoms every time you have sex

For more information on latex condoms, see "Male Latex Condoms and Sexually Transmitted Diseases" (PDF).

For more information about the connection between HIV and other STDs, see "The Role of STD Testing and Treatment in HIV Prevention."

If you would like more information or have personal concerns, call CDC-INFO 24 Hours/Day at 1-800-CDC-INFO (232-4636), 1-888-232-6348 (TTY), in English, en Español.

Why is injecting drugs a risk for HIV?

At the start of every intravenous injection, blood is introduced into the needle and syringe. HIV can be found in the blood of a person infected with the virus. The reuse of a blood-contaminated needle or syringe by another drug injector (sometimes called "direct syringe sharing") carries a high risk of HIV transmission because infected blood can be injected directly into the bloodstream.

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

• using blood-contaminated syringes to prepare drugs;
• reusing water;
• reusing bottle caps, spoons, or other containers ("spoons" and "cookers") used to dissolve drugs in water and to heat drug solutions; or
• reusing small pieces of cotton or cigarette filters ("cottons") used to filter out particles that could block the needle.

"Street sellers" of syringes may repackage used syringes and sell them as sterile syringes. For this reason, people who continue to inject drugs should obtain syringes from reliable sources of sterile syringes, such as pharmacies.

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

For more information see "How can injection drug users reduce their risk for HIV infection?"

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 is very low, especially if they carefully follow universal precautions (i.e., using protective practices and personal protective equipment to prevent HIV and other blood-borne infections). It is important to remember that casual, everyday contact with an HIV-infected person does not expose health care workers or anyone else to HIV. 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 infection from a needle-stick is less than 1 percent, a figure based on the findings of several studies of health care workers who received punctures from HIV-contaminated needles or were otherwise exposed to HIV-contaminated blood.

For more information on preventing occupational exposure to HIV, refer to the CDC fact sheet, "Preventing Occupational HIV Transmission to Healthcare Personnel" available at www.cdc.gov/hiv/resources/factsheets/hcwprev.htm.

Although the most important strategy for reducing the risk of occupational HIV transmission is to prevent occupational exposures, plans for postexposure management of health care personnel should be in place. For guidelines on management of occupational exposure, refer to the June 29, 2001 Morbidity and Mortality Weekly Report, "Updated U.S. Public Health Service Guidelines for the Management of Occupational Exposures to HBV, HCV, and HIV and Recommendations for Postexposure Prophylaxis" available at www.cdc.gov/mmwr/preview/mmwrhtml/rr5011a1.htm.

For more information on HIV and health care workers, visit the health care worker section of the CDC National Prevention Information Network (NPIN) Web site at /www.cdcnpin.org/scripts/population/hcw.asp, or call NPIN at 1-800-458-5231.

To find a testing site near you, visit the National HIV Testing Resources web site at www.hivtest.org.

Are patients in a health care setting at risk of getting HIV?

Although HIV transmission is possible in health care settings, it is extremely rare. Medical experts emphasize that the careful practice of infection control procedures, 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.

For more information on preventing occupational exposure to HIV, refer to the CDC fact sheet, "Preventing Occupational HIV Transmission to Healthcare Personnel" available at www.cdc.gov/hiv/resources/factsheets/hcwprev.htm.

In 1990, the CDC reported on an HIV-infected dentist in Florida who apparently infected some of his patients while doing dental work. Studies of viral DNA sequences linked the dentist to six of his patients who were also HIV-infected. The CDC has not yet been able to establish how the transmission took place. No additional studies have found any evidence of transmission from provider to patient in health care settings.

CDC has documented rare cases of patients contracting HIV in health care settings from infected donor tissue. Most of these cases occurred due to failures in following universal precautions and infection control guidelines. Most also occurred early in the HIV epidemic, before established screening procedures were in place.

For more information, see "Are health care workers at risk of getting HIV on the job?" or visit the health care worker section of the CDC National Prevention Information Network (NPIN) Web site at www.cdcnpin.org/scripts/population/hcw.asp, or call NPIN at 1-800-458-5231.

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

Female-to-female transmission of HIV appears to be a rare occurrence. However, there are case reports of female-to-female transmission of HIV. The well documented risk of female-to-male transmission of HIV shows that vaginal secretions and menstrual blood may contain the virus and that mucous membrane (e.g., oral, vaginal) exposure to these secretions has the potential to lead to HIV infection.

In order to reduce the risk of HIV transmission, women who have sex with women should do the following:

• Avoid exposure of a mucous membrane, such as the mouth, (especially non-intact tissue) to vaginal secretions and menstrual blood.
• Use condoms consistently and correctly each and every time for sexual contact with men or when using sex toys. Sex toys should not be shared. No barrier methods for use during oral sex have been evaluated as effective by the FDA. However, natural rubber latex sheets, dental dams, cut open condoms, or plastic wrap may offer some protection from contact with body fluids during oral sex and possibly reduce the risk of HIV transmission.
• Know your own and your partner?s HIV status. This knowledge can help uninfected women begin and maintain behavioral changes that reduce the risk of becoming infected. For women who are found to be infected, it can assist in getting early treatment and avoiding infecting others.

For more information refer to "HIV/AIDS among Women Who Have Sex with Women."

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

A risk of HIV transmission does exist if instruments contaminated with blood are either not sterilized or disinfected or are used inappropriately between clients. CDC recommends that single-use instruments intended to penetrate the skin be used once, then disposed of. Reusable instruments or devices that penetrate the skin and/or contact a client's blood should be thoroughly cleaned and sterilized between clients.

View the CDC fact sheet on the sterilization of patient-care equipment and HIV (from the CDC Division of Healthcare Quality Promotion Web site).

Personal service workers who do tattooing or body piercing should be educated about how HIV is transmitted and take precautions to prevent transmission of HIV and other blood-borne infections in their settings.

If you are considering getting a tattoo or having your body pierced, ask staff at the establishment what procedures they use to prevent the spread of HIV and other blood-borne infections, such as the hepatitis B virus. You also may call the local health department to find out what sterilization procedures are in place in the local area for these types of establishments.

Visit the CDC Web site for links to the 50 U.S. state health departments.

Can I get HIV from a bite?

Human Bite:

In 1997, CDC published findings from a state health department investigation of an incident that suggested blood-to-blood transmission of HIV by a human bite. There have been other rare reports in the medical literature in which HIV appeared to have been transmitted by a bite. Severe trauma with extensive tissue tearing and damage and presence of blood were reported in each of these instances. Biting is not a common way of transmitting HIV. In fact, there are numerous reports of bites that did not result in HIV infection.

Non-Human Bite:

HIV is a virus that infects humans and thus cannot be transmitted to or carried by non-human animals. The only exception to this is a few chimpanzees in laboratories that have been artificially infected with HIV. Because HIV is not found in non-human animals it is not possible for HIV to be transmitted from an animal bite, such as from a dog or cat.

Some animals can carry viruses that are similar to HIV, such as FIV (Feline Immunodeficiency Virus) found in cats or SIV (Simian Immunodeficiency Virus) found in apes. These viruses can only exist in their specific animal host and are not transmissible to humans.

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

No. HIV is not transmitted by day-to-day contact in the workplace, schools, or social settings. HIV is not transmitted 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, or pets.

HIV is not an airborne or food-borne virus, and it does not live long outside the body. HIV can be found in the blood, semen, or vaginal fluid of an infected person. The three main ways HIV is transmitted are

• through having sex (anal, vaginal, or oral) with someone infected with HIV.
• through sharing needles and syringes with someone who has HIV.
• through exposure (in the case of infants) to HIV before or during birth, or through breast feeding.

For more information about HIV transmission, see "HIV and Its Transmission."

Although contact with blood and other body substances can occur in households, transmission of HIV is rare in this setting. A small number of transmission cases have been reported in which a person became infected with HIV as a result of contact with blood or other body secretions from an HIV-infected person in the household. For information on these cases refer to the May 20, 1994 Morbidity and Mortality Weekly Report, "Human Immunodeficiency Virus Transmission in Household Settings -- United States" available at www.cdc.gov/mmwr/preview/mmwrhtml/00030972.htm.

Persons living with HIV and persons providing home care for those living with HIV should be fully educated and trained regarding appropriate infection-control procedures.

You may view and/or download "Caring for Someone with AIDS at Home" at www.cdc.gov/hiv/pubs/brochure/careathome.htm.

For more information on about providing home care or living with a person who is HIV-infected, visit the CDC National Prevention Information Network (NPIN) Web site at www.cdcnpin.org, or call NPIN at 1-800-458-5231.

Can I get HIV from mosquitoes?

No. From the start of the HIV epidemic there has been concern about HIV transmission from biting and bloodsucking insects, such as mosquitoes. However, studies conducted by the CDC and elsewhere have shown no evidence of HIV transmission from mosquitoes or any other insects -- even in areas where there are many cases of AIDS and large populations of mosquitoes. Lack of such outbreaks, despite intense efforts to detect them, supports the conclusion that HIV is not transmitted by insects.

The results of experiments and observations of insect biting behavior indicate that when an insect bites a person, it does not inject its own or a previously bitten person's or animal's blood into the next person bitten. Rather, it injects saliva, which acts as a lubricant so the insect can feed efficiently. Diseases such as yellow fever and malaria are transmitted through the saliva of specific species of mosquitoes. However, HIV lives for only a short time inside an insect and, unlike organisms that are transmitted via insect bites, HIV does not reproduce (and does not survive) in insects. Thus, even if the virus enters a mosquito or another insect, the insect does not become infected and cannot transmit HIV to the next human it bites.

There also is no reason to fear that a mosquito or other insect could transmit HIV from one person to another through HIV-infected blood left on its mouth parts. Several reasons help explain why this is so. First, infected people do not have constantly high levels of HIV in their blood streams. Second, insect mouth parts retain only very small amounts of blood on their surfaces. Finally, scientists who study insects have determined that biting insects normally do not travel from one person to the next immediately after ingesting blood. Rather, they fly to a resting place to digest the blood meal.

Can I get HIV while playing sports?

There are no documented cases of HIV being transmitted during participation in sports. The very low risk of transmission during sports participation would involve sports with direct body contact in which bleeding might be expected to occur.

If someone is bleeding, their participation in the sport should be interrupted until the wound stops bleeding and is both antiseptically cleaned and securely bandaged. There is no risk of HIV transmission through sports activities where bleeding does not occur.