HIV Transmission

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How HIV Spreads

Many people still do not understand how HIV is passed, or transmitted, from one person to another. Knowing the basics helps you avoid becoming HIV-positive. If you are HIV-positive, these basics help you avoid exposing someone else to HIV.

The spread of HIV can be prevented! There are ways to avoid, or at least reduce, contact with body fluids that transmit HIV. This fact sheet explains how.

HIV is transmitted, or spread, through contact with the following body fluids:

  • Blood (including menstrual blood and any blood in saliva, urine, and feces)
  • Semen ("cum") and other male sexual fluids ("pre-cum")
  • Vaginal fluids
  • Breast milk

HIV is also spread through contact with these body fluids; however, usually only health care workers come into contact with these fluids. These fluids are:

  • Cerebrospinal fluid around the brain and spinal cord
  • Synovial fluid around the joints
  • Amniotic fluid around a developing fetus (or baby in the womb)

HIV is not spread through contact with these body fluids:

  • Sweat
  • Tears
  • Saliva (spit)
  • Feces (poop)
  • Urine (pee)

In other words, you cannot get HIV by touching or hugging someone who is living with HIV, kissing someone living with HIV, drinking or eating from the same cups or utensils as a person living with HIV, or by using a toilet also used by someone living with HIV.

Methods of Transmission

Today, the most common ways HIV is passed from one person to another are:

Re-using and Sharing Needles for Injecting Drugs

  • Injecting Drugs (including steroids or hormones): Many people get HIV when they share the equipment used to inject heroin, methamphetamines, steroids, hormones, or other drugs. Re-using syringes, needles, water, spoons, "cookers," or "cottons" can spread HIV. Be sure to use new syringes and needles only from reliable sources, such as needle exchange programs or pharmacies. Many cities offer free needle and syringe exchange programs. For more information, see our fact sheet on Cleaning Equipment for Injecting Drugs.
  • Tattoos or Body Piercings: Tattoos or body piercings should always be done by a licensed professional whose equipment, including ink, is sterile. The US Centers for Disease Control and Prevention (CDC) recommends instruments be used only once and then thrown away. Reusable instruments must be sterilized between uses. Using alcohol to clean instruments is not enough. Proper sterilization involves having instruments steam sterilized, or autoclaved.

Unprotected/Unsafe Sex

Every sexual act (oral, anal, or vaginal) involving sexual fluids has at least some risk. Barriers, such as condoms (male and female), dental dams (thin squares of latex), and latex or nitrile gloves help reduce risk substantially

For people living with HIV, taking HIV drugs can also reduce the risk of HIV transmission to others. HIV drugs can reduce their viral load to undetectable levels. This makes it virtually impossible for their blood, vaginal fluids, breast milk, and semen (cum) to pass HIV on to others. For people who are HIV-negative, taking HIV drugs as pre-exposure prophylaxis (PrEP) can reduce their risk of becoming HIV+ if they are exposed to HIV. For more information on PrEP, please see our fact sheet on PrEP for women.

These methods are part of what is known as HIV treatment as prevention (TasP). TasP does not prevent transmission of other sexually transmitted infections or diseases (STIs or STDs). Please see our fact sheet on TasP for more information.

Unsafe sex (sex without condoms, other barriers, or treatment-as-prevention methods) puts you and/or your partner at risk for HIV or other STIs or STDs. Safer sex (sex using condoms, other barriers, and/or treatment-as-prevention methods consistently and correctly) is the most effective way to protect you and your partner.

Which common sexual activities are most likely to cause HIV transmission when safer sex is not used? Listed from most to least risky:

  1. Receptive anal sex ("bottoming"): Taking a penis through one's anus and into one's rectum remains the most risky activity. This is due to the likelihood of small tears in the rectum that allow semen ("cum") to have direct contact with the bloodstream.
  2. Receptive vaginal intercourse: This refers to taking a penis into one's vagina. HIV is transmitted from men to women much more easily than from women to men.
  3. Insertive anal sex ("topping"): Putting one's penis into someone else's anus and rectum can expose you to HIV
  4. Insertive vaginal intercourse: Putting one's penis into a vagina, especially when the woman is menstruating, can expose you to HIV
  5. Giving oral sex: Using one's mouth to lick, suck, or bite another person's genitals (penis, vagina, or anus) can expose you to HIV. Swallowing semen ("cum"), licking menstrual blood, and having bleeding gums, mouth ulcers, or gum disease will increase your risk of getting HIV.
  6. Receiving oral sex: Having your genitals licked, sucked, or bitten is less risky than giving oral sex. However, you can get HIV from your partner, especially if your partner has bleeding gums, mouth ulcers, or gum disease.
  7. Sharing sex toys without sterilizing them or using a new condom: This can allow HIV to be transmitted from the first partner to the next one who uses the toy
  8. Mutual masturbation (hand jobs), fingering, and fisting (using a hand to penetrate the anus or vagina): These are extremely low risk, as long as your hand has no open cuts or sores

Sexual assault or rape can result in transmission if the attacker is living with HIV. The risk increases when rape involves anal penetration, force, and/or multiple attackers. Some forced sexual acts involving wounds can place a victim at very high risk.

Survivors of sexual assault or rape who do not already have HIV should be routinely offered PEP (post-exposure prophylaxis; also called non-occupational PEP, or nPEP) in emergency rooms. This 28-day treatment with HIV drugs greatly reduces the chances of acquiring HIV. PEP is another form of TasP.

PEP must be started within the first 72 hours of exposure to be effective. The earlier treatment is started, the more effective it will be. If PEP is not offered in the emergency room or clinic after a rape or sexual assault, do not be afraid to ask for it.

Perinatal Transmission

Women living with HIV can pass the virus to their babies while pregnant, during birth, or by breastfeeding. This is called perinatal or vertical transmission, and is also known as mother-to-child transmission. The good news is that medical care and HIV drugs given during pregnancy can almost eliminate the risk of a baby getting HIV from its mother.

In resource-rich countries like the US, it is recommended that mothers living with HIV not breastfeed their babies. In other countries, where formula is unavailable or clean water sources are unreliable, it is recommended that mothers breastfeed their babies exclusively (no mixed feeding, such as some breast milk and some gripe or sugar water). It is also important not to feed your baby food that has been chewed by someone who is living with HIV (pre-masticated). This can transmit HIV to your child. For more information, see our fact sheet on Pregnancy and HIV.

Other Types of Transmission

In the past, HIV was spread by transfusion with blood products, such as whole blood or the "factor" used by hemophiliacs. Many people acquired HIV this way. The blood supply is now much more strictly tested and controlled in most countries. The odds of acquiring HIV from receiving blood or blood factor in countries like the US, the UK, and Canada are vanishingly low. In the US, for example, a person is more likely to be killed by a lightning strike than to acquire HIV from a blood transfusion. Only about 1 in 2 million donations might carry HIV. However, there are still several countries that do not screen all blood donations for HIV.

It is also possible to get HIV from skin grafts or transplanted organs taken from people living with HIV. Again, the risk is considered very low, as these 'body products' are required to be strictly tested in the same way as blood products. Semen donations collected by sperm banks for artificial insemination are also considered 'bodily products' and strictly tested in high-resource countries. Private semen samples that are not processed by sperm banks or similar organizations are not subject to the same testing. It is important for anyone receiving a private donor's sperm for artificial insemination to have the donor tested for HIV.

Some people, mostly health care workers, are infected through needle sticks with infected blood, or through other medical accidents. This is a very small percentage of overall infections. According to the CDC, only three in every 1,000 exposures to HIV-infected blood at work, if left untreated, will result in HIV infection. When exposed to fluid or body products that may be infected while on the job, health care workers should be offered occupational post-exposure prophylaxis (oPEP) immediately.

If you are getting breast milk from a milk bank, it is important to ask if the bank tests the milk for HIV. Also, if your baby is getting breast milk from a wet nurse, it is important to make sure that she tests negative for HIV before giving her milk to your baby.

Rare Types of Transmission

There are a few isolated cases of people becoming HIV-positive from using a razor that had just been used by a person living with HIV, or from using a toothbrush immediately after the toothbrush was used by someone living with HIV, or in other unexpected ways. One case of transmission occurred when two people, both of whom had bleeding gums and/or open sores in their mouths, engaged in deep or "French" kissing. In this situation, they were exposed not only to each other's saliva (which does not carry HIV), but also to each other's blood (which can transmit HIV). To be safe, always avoid direct contact with blood and sexual fluids.

Avoiding Transmission

HIV cannot be transmitted except when certain body fluids are exchanged. You can greatly reduce the risk of transmission by:

  • Knowing your HIV status so you can take steps to avoid spreading HIV if you are living with HIV; for more information, see our fact sheet on HIV Testing
  • Practicing safer sex including taking PrEP
  • Having sex without condoms or other barriers only if you and your partner are both HIV-negative and in a monogamous relationship
  • Abstaining from sex
  • Not injecting drugs
  • Using new or clean needles and other equipment for any injections
  • Staying on your HIV drug regimen if you are living with HIV. This will keep your viral load as low as possible. Keeping your viral load low will reduce the risk of your passing HIV to others (sexual partners, mother-to-child).

You do not need to be afraid of getting or passing HIV by casual contact. Remember, HIV is not transmitted by:

  • Hugs
  • Dancing
  • Sharing food or drinks
  • Using a toilet, shower, bath, or bed
  • Kissing (between people with no significant dental problems)
  • Sharing exercise equipment
  • Bug bites

Additional Resources

Select the links below for additional material related to HIV transmission.

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