HIV is a virus that only transmits through specific bodily fluids, including blood, semen, and vaginal fluids. Treatment can now reduce levels of virus in a person with HIV so effectively that it becomes undetectable. When this happens, transmission cannot occur.

There are many myths about HIV transmission, and it is important to know the facts. Understanding how HIV spreads and cannot spread helps prevent transmission and reduces the discrimination and stigma relating to HIV.

The number of new HIV diagnoses and the impact of the virus in the United States are decreasing thanks to effective preventive measures and treatments.

For example, antiretroviral therapy can reduce the amount of virus in the body to undetectable levels. When this happens, the virus cannot harm the body or pass on to another person.

This article looks at how HIV transmits, how it cannot, and how to keep it from passing on.

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In most cases, people contract HIV through anal or vaginal sex or through sharing drug injection equipment, such as needles or syringes.

HIV can only transmit through certain body fluids:

  • blood
  • semen
  • preseminal fluid
  • rectal fluids
  • vaginal fluids
  • breast milk

Blood can carry more of the virus than other bodily fluids, so the greatest likelihood of transmission involves exposure to blood containing the virus.

However, HIV does not pass on through all contact with fluids carrying the virus. For transmission to occur, the fluid must come into contact with damaged tissue, the bloodstream, or mucous membranes, such as those in the genitals, rectum, or mouth.

If blood containing HIV comes into direct contact with another person’s bloodstream, such as through an injection with a shared needle, this is very likely to transmit the virus.

HIV can transmit to a baby during pregnancy, birth, or breastfeeding. However, this is less common due to modern preventive measures and treatments.

According to the Centers for Disease Control and Prevention (CDC), HIV cannot transmit through:

  • insect bites, including those from mosquitoes and ticks
  • the air
  • contact with saliva, tears, or sweat
  • shaking hands, hugging, or closed-mouth kissing
  • sharing toilets, dishes, or utensils
  • eating food that someone with HIV has handled or prepared
  • sexual activities that do not involve fluid exchange, such as touching

HIV cannot survive long outside the body, so it does not transmit via surfaces.

Additionally, the risks of contracting the virus through other methods of exposure, such as biting, scratching, and thrown bodily fluids, are either very small or nonexistent.

There is also little to no risk of contracting HIV via:

  • Oral sex: However, having mouth ulcers, genital sores, or bleeding gums can increase the risk of transmission, as can having existing sexually transmitted infections (STIs).
  • Workplace exchanges: However, a puncture from a needle or another sharp object that contains the virus can lead to transmission.
  • Blood transfusion or donated organs: Current screening practices in the U.S. are safe and undergo stringent regulation, making this transmission highly unlikely.
  • Deep, open-mouth kissing: Transmission in this way is very rare, but it can occur if both people have oral sores or bleeding gums.
  • Tattoos and body piercings: There have been no reports of transmission from tattoos or piercings in the U.S., although it is possible if the equipment or ink has been in contact with someone else’s blood.

For more in-depth information and resources on HIV and AIDS, visit our dedicated hub.

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Anyone can contract HIV, but several factors increase the risk. These include:

  • sharing equipment for injecting drugs
  • getting a tattoo with a shared needle or shared ink
  • having anal or vaginal sex without a condom
  • having an STI
  • having frequent exposure to fluids containing the virus, such as in laboratory, medical, or emergency settings
  • using drugs and alcohol, which can impair judgment
  • having exposure to the virus during childbirth, pregnancy, or breastfeeding

HIV affects certain populations more than others in the U.S., including:

  • Black and Latinx people
  • cisgender and transgender males who have sex with cisgender males
  • transgender females

In 2019, the latest year for which figures are available, males who had sex with other males received 65% of all new HIV diagnoses in the U.S. Anal sex without a condom was the most likely route of transmission because the risk of tissue damage is high.

HIV also affects more people who are Black or Latinx due to systemic inequity in healthcare and social and economic marginalization as well as other ingrained barriers.

In 2019, Black people received 41% of new HIV diagnoses in the U.S., while Hispanic and Latino individuals received 29% of those diagnoses, and white people received 25%.

The prevalence of HIV differs by region of the U.S. In 2019, the South had the largest number of people living with HIV and the highest rate of new cases. The rate is the number of cases per 100,000 people. However, in terms of its population size, the Northeast had the largest rate of individuals living with HIV.

What about breastfeeding?

According to the World Health Organization (WHO), a person who has acquired HIV and receives no treatment has a 15 to 45% chance of passing on the virus to their infant during labor, delivery, or breastfeeding. This is due to contact with relevant body fluids.

Antiretroviral therapy can reduce the chances of transmission to below 2% during pregnancy. However, breastfeeding while receiving antiretroviral therapy is not advisable in the U.S., say the CDC and the American Academy of Pediatrics (AAP).

Social factors

Some social factors that influence a person’s risk of HIV transmission include:

  • access to education about HIV transmission and prevention
  • access to affordable healthcare
  • discrimination and stigma in healthcare and society at large
  • reduced negotiating power due to sex, gender, and financial or other status factors

Increased awareness of and access to antiretroviral therapy, preventive medication, and support services are effective ways to reduce the impact of HIV.

A range of effective strategies can now lower the risk of contracting HIV. These include:

  • using preexposure prophylaxis (PrEP), a preventive drug
  • never sharing needles with another person
  • using condoms during sex
  • getting frequent HIV testing as per CDC recommendations
  • using gloves and other sterile equipment in medical settings
  • taking emergency postexposure prophylaxis after possible exposure to the virus

When a person takes PrEP daily, it reduces the risk of contracting HIV via sex by about 99% and via needles and syringes by about 74%.

The Preventive Services Task Force updated its HIV guidelines in 2019. It now recommends that only people who have recently received negative results from HIV screening be candidates for PrEP. Individuals with a high risk of exposure to the virus should take PrEP once per day.

Anyone with HIV who is pregnant or plans to be should discuss ways to mitigate the risk of transmission with their healthcare professional, including the choice of whether to breastfeed.

Due to advances in prevention and treatment, the number of new HIV cases in the U.S. has decreased by more than two-thirds since the mid-1980s.

Undetectable equals untransmittable

Using antiretroviral therapy consistently as a doctor prescribes can reduce the risk of transmission to virtually zero. It slows or stops the activity of HIV in the body.

Health experts consider the virus suppressed when someone with HIV has a viral load of 200 copies per milliliter of blood or under. It may be undetectable at this level or under, meaning it cannot transmit to others. However, it is important to keep following a treatment plan and attend regular check-ups to ensure that the viral load remains undetectable.

Many people with HIV experience no symptoms. A person can only know their HIV status by taking a test.

The CDC recommends that everyone aged 13–64 years have at least one HIV test.

Early testing, diagnosis, and treatment are the most effective ways to stop the progression and transmission of the virus.

Frequent testing is an inexpensive and effective way to stop the spread of HIV. It is especially important to test:

  • when planning to become pregnant
  • after becoming pregnant
  • before having sex with a new partner

People with a high risk of contracting the virus, including gay and bisexual males who are sexually active and sex workers, may wish to undergo testing every 3–6 months. Individuals whose partners have HIV, those who share drug injection equipment, and those who have had hepatitis, tuberculosis, or an STI should undergo testing once a year or more.

What are the odds of contracting HIV?

The CDC provides an online risk estimation tool featuring up-to-date evidence in its analysis. It helps a person determine their chances of contracting HIV from various activities.

HIV can only transmit in certain situations through contact with blood, rectal fluids, vaginal fluids, breast milk, and semen or preseminal fluid.

There are many ways to reduce the risk of contracting HIV, including using condoms when having sex, taking PrEP, and never using shared needles.

In the U.S., HIV has had a disproportionate impact on certain groups, including Black and Latinx people and cisgender and transgender males who have sex with cisgender males.

However, with modern antiretroviral therapy, fewer people contract HIV. Those with continuous access to this treatment are able to live long, healthy lives, and the risk of transmission is significantly reduced, often to zero.

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