HIV is a global health issue that affected about 38 million people worldwide in 2020. Individuals have varying chances of contracting HIV due to certain sexual behaviors and other factors.

The World Health Organization (WHO) states that at the end of 2020, approximately 38 million people were living with HIV worldwide. And according to, around 1.2 million individuals in the United States have contracted HIV.

In this article, we discuss how certain behaviors affect the risk of HIV transmission.

We also cover methods of preventing HIV transmission, what to do if someone has concerns about HIV exposure, and guidance for finding support.

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Merely describing a person’s risk of acquiring HIV as high or low is vague. These terms lack the necessary quantifiable information to accurately assess the risk of specific behaviors.

However, the Centers for Disease Control and Prevention (CDC) provide the following risk estimates for HIV transmission based on different types of exposure:

Type of exposureRisk per 10,000 exposuresRisk per single exposure (percentage)
Receptive anal intercourse1381.38%
Insertive anal intercourse110.11%
Receptive penile-vaginal intercourse80.08%
Insertive penile-vaginal intercourse40.04%
Receptive oral intercourseLOWLOW
Insertive oral intercourseLOWLOW
Maternal-to-child transmission (MTCT) or vertical transmissionNA15–45% without any medical intervention
Needle-sharing during injection drug use630.63%
Blood transfusion9,25093%

HIV, or human immunodeficiency virus, is a virus that destroys immune cells.

As a result, HIV weakens the body’s immune system, leaving the body vulnerable to infections.

An HIV infection can eventually lead to AIDS if a person does not receive treatment.

HIV affects people of all ages, races, and ethnicities, genders, sexual orientations, and socioeconomic backgrounds.

Of the 38 million people worldwide living with HIV in 2020:

  • 36 million were adults
  • 1.7 million were children under the age of 15
  • 20.6 million lived in eastern and southern Africa
  • 4.7 million lived in western and central Africa
  • 5.7 million lived in Asia and the Pacific
  • 2.2 million lived in Europe and North America

Learn more about HIV and AIDS here.

HIV can transmit through different bodily fluids, including:

  • blood
  • semen and pre-seminal fluid
  • vaginal secretions
  • rectal fluids
  • breast milk

HIV transmission only occurs if the bodily fluids of a person with detectable levels of HIV enter the bloodstream of a person who does not have HIV.

HIV can enter the bloodstream through:

  • cuts or broken skin
  • open sores
  • direct injection
  • mucous membranes, such as those found in the mouth, rectum, vagina, and tip of the penis

HIV can also pass from the biological parent to the child during pregnancy. This is called vertical transmission.

HIV is not transmitted through:

  • insects
  • air or water
  • saliva, tears, or sweat
  • toilet seats
  • day-to-day contact, such as shaking hands, hugging, or kissing

Some activities carry a higher chance of contracting HIV than others.

Anal sex

The CDC notes that anal intercourse, regardless of a person’s gender identity or sexual orientation, is the riskiest type of sex for HIV transmission.

The chance of contracting HIV via anal sex is as follows:

  • receptive anal intercourse: 1.38%
  • insertive anal intercourse: 0.11%

Although both can contract HIV via anal sex, the receptive partner has a higher chance. This is because the lining of the rectum is thin and easily injured.

The insertive partner may contract HIV via the urethra or small cuts, scratches, and open sores on the penis.

Having a rectal infection like herpes may also increase the risk of transmission.

Vaginal sex

Either sexual partner can contract HIV via vaginal sex.

HIV can be contracted through the lining of the vagina and cervix if their sexual partner’s bodily fluids, such as semen and pre-seminal fluid, carry HIV.

Limited research is available on the rates of HIV transmission via insertive penile sex in a neovagina.

HIV can also be contracted from the vaginal fluid and blood through the opening of the penis, the foreskin, and small cuts and scratches or open sores.

The chances of contracting HIV via vaginal sex are as follows:

  • receptive penile-vaginal intercourse: 0.08%
  • insertive penile-vaginal intercourse: 0.04%

Having a vaginal infection may also increase the risk of transmission.

Oral sex

The CDC note that there is little to no risk of contracting HIV via oral sex.

Mouth-to-penis oral sex may carry the highest chance of transmitting HIV, but the chances are still very low.

Factors that may increase the chance of contracting HIV via oral sex include:

Other sexual activities

Although it is possible to transmit HIV through the following activities, the chance is low:

  • Fingering: To lessen the chance of transmission, a person should ensure they have clean hands and trimmed fingernails so as not to damage the wall of the anus or vagina.
  • Sex toy use: HIV transmission is possible through sharing sex toys, such as dildos, vibrators, and butt plugs. A person should clean their sex toys between each use and avoid sharing them.

Transmitted during pregnancy

Research has found that the rate of transmission during pregnancy, labor, delivery, and breastfeeding or chestfeeding is 15-45% without any medical intervention.

However, the risk is even lower if the pregnant person takes antiretroviral (ART) drugs during the pregnancy and breastfeeding or chestfeeding.

Transmission through needles

HIV transmission through needles occurs when a person who does not have HIV uses the same needle or syringe as someone who is HIV positive.

Used syringes usually contain residual fluid, such as blood, on the needle or nozzle.

When people who use injectable drugs share needles and syringes, they risk exposing themselves to blood containing infectious microbes.

According to the CDC, the chance of transmission via shared needle use is 0.63%.

People who seek help for substance use can contact the Substance Abuse and Mental Health Services Administration (SAMHSA) at 1-800-662-4357 or visit their website.

STIs transmit from person to person through sexual activities, such as anal, vaginal, or oral sex.

Examples of STIs include:

STIs can also lead to open sores on the skin and the mucous membranes of the vagina, penis, anus, and rectum. HIV can enter the bloodstream through an open sore or a break in the skin.

Certain behaviors can increase a person’s risk of STIs and HIV. These behaviors include:

  • having sex without a condom or other barrier method
  • having sex with multiple partners
  • having sex while under the influence of drugs or alcohol
  • using injectable drugs

People living with HIV can use the following to prevent transmitting it to others:

  • Preexposure prophylaxis (PrEP): This daily pill contains two antivirals: Tenofovir and emtricitabine. When a person takes it daily, PrEP can reduce the risk of acquiring HIV through sex by 99%. PrEP is for those who do not have HIV but are at a high risk of contracting it.
  • Postexposure prophylaxis (PEP): ART drugs that can prevent HIV infection after potential exposure. The CDC recommend starting PEP within 72 hours of a recent potential HIV exposure.

HIV treatment as prevention

People with HIV can take ART to lower their chance of transmitting HIV to others.

ART reduces the quantity of HIV in the body, or viral load, and keeps it at a low level.

The term “viral load” refers to the number of HIV copies per milliliter of blood.

Healthcare professionals define successful viral suppression as having a viral load of fewer than 200 copies of HIV per milliliter of blood. Achieving and maintaining viral suppression significantly reduces the risk of HIV transmission.

Other ways to prevent HIV transmission include:

  • using a condom or other barrier method during sex
  • reducing the number of sexual partners
  • getting vaccinated against other STIs, such as HPV and hepatitis B
  • avoiding using injectable drugs, if possible
  • if using injectable drugs, avoiding sharing needles and syringes
  • following all workplace safety protocols

People can speak with a doctor to learn more about their individual risk of contracting HIV.

Anyone concerned about HIV exposure should contact a healthcare professional or a local emergency room to get testedand receive PEP.

The CDC note that healthcare professionals who suspect they may have experienced exposure to HIV in their workplace can call the PEPline at 1-888-448-4911.

HIV discrimination is the unjust treatment of a person based on their real or perceived HIV status.

Other people who may encounter HIV discrimination include family members, friends, and partners of a person living with HIV.

The following support services are available to HIV-positive people:

People can search for HIV and AIDS resources in their area using A Positive Life, an online resource.

A person should consult a healthcare professional if they are concerned about HIV exposure.

People who take medication for HIV can plan on attending follow-up appointments with their doctor every 6 months if they are well controlled and stable.

Certain behaviors can increase a person’s chance of contracting HIV. HIV transmits through bodily fluids, such as blood, semen, and breast milk.

A person who has anal, vaginal, or oral sex with a person that has detectable levels of HIV has a less than 2% chance of contracting it per sexual act.

People can use preventive measures such as PREP, PEP, and ART to lower their chance of contracting HIV through sex. They can also use condoms or other barrier methods.

Read this article in Spanish.