HIV after exposure? Transmission, risk factors and more


HIV is a virus that weakens your immune system by killing CD4 cells, which are a type of immune cell. People living with untreated HIV are more vulnerable to the disease.

HIV can develop into AIDS if left untreated. The World Health Organization estimated at the end of 2020 that about 37.7 million people are living with HIV around the world.

HIV is transmitted between people through bodily fluids. Unprotected anal or vaginal sex and sharing needles are common ways for people to get HIV. People can also pass HIV to their babies during pregnancy or while breastfeeding.

HIV can be transmitted even with a single brief exposure. The authors of a 2014 review of studies estimated the risks of infection for various types of exposure. Based on their data, the table below shows the estimated risk of contracting HIV for a single exposure event:

There are a number of factors that can influence your chances of getting HIV after exposure. Read on as we take a look at these factors and what to do if you think you’ve been exposed.

HIV is transmitted between humans through bodily fluids. Here are the most common modes of transmission.

Sex without a condom or barrier method

HIV can be transmitted by:

  • some blood
  • sperm
  • pre-seminal fluid (pre-ejaculate)
  • rectal fluids
  • vaginal fluids

It is possible to get HIV when any of these fluids from a person living with HIV come in contact with your mucous membranes, such as those found in:

Sharing needles

Needles can pass small amounts of blood from person to person, even if no blood is visible on the syringe. Sharing needles also increases the risk of developing other illnesses such as hepatitis B or C.

HIV and pregnancy

HIV can be passed from parent to child during pregnancy, during childbirth or through breast milk. Parent-to-child transmission is the The most common how children get HIV.

There are ways for a pregnant person living with HIV to avoid passing the virus on to their child. According to CDC, if a pregnant person takes anti-HIV drugs throughout pregnancy and childbirth, and the baby is given anti-HIV drugs for 4-6 weeks after birth, the risk of transmission is less than 1 %.

The following factors influence your chances of developing HIV after exposure.

Viral load

Viral load is a measure of the amount of virus in a person’s blood. The higher a person’s viral load, the higher their chance of passing HIV to another person. People who take HIV medicines may suppress HIV to the point where it is undetectable after 7 to 12 months and therefore not transmissible.

Multiple exhibitions

Multiple exposures to HIV increase the risk of infection. For example, if you have sex without a condom or other barrier method with someone who is HIV positive several times, your risk of contracting HIV increases.

Multiple sexual partners

Having more than one sex partner increases the chances that one of your partners will be infected with HIV.

Have an STI

You are more likely to pass HIV when you have genital ulcers or urethritis.

Having other sexually transmitted infections (STIs) like gonorrhea or syphilis suggests having barrier-free sex with at least one sexual partner. Having sex without a barrier method increases the risk of developing HIV infection.

People who do not know they are HIV positive

It is estimated that about 1 in 7 people living with HIV in the United States do not know they have the virus.

People who don’t know they have HIV are less likely to take precautions to prevent transmission to others. They probably don’t take any medicine to suppress the virus either.

If you are not currently infected with HIV, you can prevent your risk of infection by:

  • discussing HIV and STIs with your partner before engaging in sexual activity
  • use a barrier method whenever you engage in sexual activity
  • avoid sharing needles
  • discuss post-exposure prophylaxis (PEP) with your doctor if you may have been exposed to HIV in the past 72 hours
  • getting tested regularly for other STIs or before engaging in sexual activity with a new partner

If you have HIV you can prevent passing it on to others by:

  • discussing HIV and STIs with your partner before engaging in sexual activity
  • use a barrier method whenever you engage in sexual activity
  • take your medications as prescribed
  • avoiding sharing needles or drug injection equipment
  • get your viral load tested regularly as recommended by your doctor

Pre-exposure prophylaxis (PrEP)

Pre-exposure prophylaxis (PrEP) is a drug that reduces by about 99 percent and injected drugs by about 74 percent when used as prescribed. If you are going to take this medicine you will need to consider how long you need to take it before it becomes effective.

If you think you have been exposed to HIV, here is what you can do.

Speak with a healthcare professional

A healthcare professional can advise you on available tests and let you know if you qualify for PEP.


It is important to get tested if you think you have been exposed to HIV so that you can start treatment as soon as possible.

HIV tests cannot immediately detect infection. The window period during which a test can correctly identify a positive infection varies depending on the type of test used, but it is at least 10 days after the exhibition.

Post-exposure prophylaxis

Post-exposure prophylaxis (PEP) is a drug treatment that must be taken within 72 hours of exposure, and it can greatly reduce your chances of developing HIV.

The Centers for Disease Control and Prevention (CDC) recommends that anyone between the ages of 13 and 64 have at least one HIV test. It is also essential to get tested after potential exposures.

Types of tests

There are three types of tests used to diagnose HIV:

  • Nucleic acid test (NAT). This test looks for the virus itself in your blood. It is used for people who have symptoms early or have been at high risk.
  • Antibody test. An antibody test is usually done with a blood test, a finger prick, or with oral fluids. The test looks for antibodies made by your immune system to protect you against HIV.
  • Antigen / antibody test. This is usually done with a blood test or a finger prick. It looks for both antibodies and antigens, which are proteins on the surface of the virus.

When to test

HIV tests are not accurate until a certain number of days have passed after exposure. The minimum time who must pass for each type of test is:

  • NAT: 10 to 33 days
  • Antibody test: 23 to 90 days
  • Antigen / antibody test: 18 to 45 days for a blood test or 18 to 90 days for a finger prick

How often to test

If your test is negative, you should retest at the end of your window period.

According to CDC, if your test comes back negative after your window window and you have had no further possible exposure during your window window, then you do not have HIV.

If you think you have been exposed to HIV, it is a good idea to see a healthcare professional as soon as possible. They can walk you through the testing process, let you know if you are eligible for post-exposure prophylaxis, and answer any specific questions you have.

The chances of developing HIV after exposure depend on factors such as the method of exposure, the viral load of the infected person and the number of exposures you have had. It is possible to develop HIV after a single exposure, although this is statistically unlikely.


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