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HIV Transmission

March 25, 2010

How is HIV passed from one person to another?

HIV can be detected in several fluids and tissue of a person living with HIV. It is important to understand however, that finding a small amount of HIV in a body fluid or tissue does not mean that HIV is transmitted by that body fluid or tissue. Only specific fluids (blood, semen, vaginal secretions, and breast milk) from an HIV-infected person can transmit HIV. These specific fluids must come in contact with a mucous membrane or damaged tissue or be directly injected into the blood-stream (from a needle or syringe) for transmission to possibly occur.

In the United States, HIV is most commonly transmitted through specific sexual behaviors (anal or vaginal sex) or sharing needles with an infected person. It is less common for HIV to be transmitted through oral sex or for an HIV-infected woman to pass the virus to her baby before or during childbirth or after birth through breastfeeding or by prechewing food for her infant. In the United States, it is also possible to acquire HIV through exposure to infected blood, transfusions of infected blood, blood products, or organ transplantation, though this risk is extremely remote due to rigorous testing of the U.S. blood supply and donated organs.

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

Some healthcare 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.

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:

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

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 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."

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."

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.

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, though it is a less common mode of transmission than other sexual behaviors (anal and vaginal 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

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

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,

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."

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

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),

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.

How can I prevent HIV transmission when using sex toys?

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

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 injecting drugs?

Yes. 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

"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?"

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:

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

For more information about the connection between HIV and other STDs, see "The Role of STD Detection 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.

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."

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."

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, or call NPIN at 1-800-458-5231.

To find a testing site near you, visit the National HIV Testing Resources Web site.

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."

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, or call NPIN at 1-800-458-5231.

Have people been infected with HIV from being stuck by needles in non-health care settings?

No. While it is possible to get infected with HIV if you are stuck with a needle that is contaminated with HIV, there are no documented cases of transmission outside of a health-care setting.

CDC has received inquiries about used needles left by HIV-infected injection drug users in coin return slots of pay phones, the underside of gas pump handles, and on movie theater seats. Some reports have falsely indicated that CDC "confirmed" the presence of HIV in the needles. CDC has not tested such needles nor has CDC confirmed the presence or absence of HIV in any sample related to these rumors. The majority of these reports and warnings appear to be rumors/myths.

CDC was informed of one incident in Virginia of a needle stick from a small-gauge needle (believed to be an insulin needle) in a coin return slot of a pay phone and a needle found in a vending machine that did not cause a needle-stick injury. There was an investigation by the local police and health department and there was no report of anyone contracting an infectious disease from these needles.

Discarded needles are sometimes found in the community. These needles are believed to have been discarded by persons who use insulin or inject illicit drugs. Occasionally the public and certain workers (e.g. sanitation workers or housekeeping staff) may sustain needle-stick injuries involving inappropriately discarded needles. Needle-stick injuries can transfer blood and blood-borne pathogens (e.g., hepatitis B, hepatitis C, and HIV), but the risk of transmission is extremely low and there are no documented cases of transmission outside of a health care setting.

CDC does not recommend routinely testing discarded needles to assess the presence or absence of infectious agents in the needles. Management of exposed persons should be done on a case-by-case basis to determine (1) the risk of a blood-borne pathogen infection in the source and (2) the nature of the injury. Anyone who is injured from a needle-stick in a community setting should contact their health-care provider or go to an emergency room as soon as possible. Antiretroviral medications given shortly after being stuck by a needle infected with HIV can reduce the risk of HIV infection. The health-care provider should then report the injury to the local or state health department. Guidance on non-occupational exposure can be found at Antiretroviral Postexposure Prophylaxis After Sexual, Injection-Drug Use, or Other Nonoccupational Exposure to HIV in the United States.

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:

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 HIV be transmitted by kissing?

It depends on the type of kissing. There is no risk from closed-mouth kissing.

There are extremely rare cases of HIV being transmitted via deep "French" kissing but in each case, infected blood was exchanged due to bleeding gums or sores in the mouth. Because of this remote risk, it is recommended that individuals who are HIV-infected avoid deep, open-mouth "French" kissing with a non-infected partner, as there is a potential risk of transferring infected blood. Summary:

Can HIV be transmitted by human bite?

It is very rare, but in specific circumstances HIV can be transmitted by a 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 human bite. Biting is not a common way of transmitting HIV, in fact, there are numerous reports of bites that did not result in HIV infection. Severe trauma with extensive tissue damage and the presence of blood were reported in each of the instances where transmission was documented or suspected. Bites that do not involve broken skin have no risk for HIV transmission, as intact skin acts as a barrier to HIV transmission.

Summary:

Can HIV be transmitted by being scratched?

No. There is no risk of transmission from scratching because there is no transfer of body fluids between individuals. Any person with open wounds should have them treated as soon as possible.

Can HIV be transmitted by being spit on by an HIV-infected person?

No. In some persons living with HIV, the virus has been detected in saliva, but in extremely low quantities. Contact with saliva alone has never been shown to result in transmission of HIV, and there is no documented case of transmission from an HIV-infected person spitting on another person.

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.

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."

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."

For more information on providing home care or living with a person who is HIV-infected, visit the CDC National Prevention Information Network (NPIN) Web site, 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.

Has HIV been transmitted from body fluids placed in restaurant food?

No incident of food being contaminated with HIV-infected blood or semen has been reported to CDC. Furthermore, CDC has received no reports of HIV infection resulting from eating food, including condiments.

HIV does not live long outside the body. Even if small amounts of HIV-infected blood or semen was consumed, exposure to the air, heat from cooking, and stomach acid would destroy the virus. Therefore, there is no risk of contracting HIV from eating food.

Has CDC discovered a mutated version of HIV that is transmitted through the air?

No, this story is not true. Many scientific studies have been conducted to examine all the possible ways that HIV is transmitted. These studies have not shown HIV to be transmitted through air, water, insects, or casual contact.




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