There is no single answer for how long HIV can survive outside the body, such as in dry blood or dry semen, as it depends on several factors. However, HIV does not survive long outside the body, and it cannot replicate without a human host.

A person can contract HIV if damaged tissue or a mucous membrane, such as those in the rectum, penis, vagina, or mouth, comes into contact with bodily fluids that contain the virus.

Only certain bodily fluids can carry HIV. These fluids include:

  • blood
  • semen
  • preseminal fluid
  • fluids in the rectum
  • fluids in the vagina
  • breast milk

This article explores the factors that affect the survival time of HIV outside the body in different fluids. It also explains how the virus can and cannot transmit.

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HIV does not typically survive for long outside the body, where it cannot replicate. The virus dies quickly upon exposure to light and air.

Therefore, contact with dried blood or semen that has been outside the body does not generally pose a risk for contracting HIV.

HIV cannot survive in the air, so people cannot contract the virus from sharing space with a person who has HIV. It is also not possible to contract HIV from sharing toilet seats, utensils, or bedding.

The length of time that the virus can survive outside the body depends on several factors, such as:

  • the type and amount of bodily fluid
  • the temperature and humidity of the environment
  • the acidity of the environment
  • whether there is exposure to sunlight

While the risk of contracting HIV from external fluids is low, the risk is high when sharing equipment to inject drugs, such as needles and syringes.

The reason for this is that the person may inject blood that contains HIV directly into their bloodstream.

Modern antiretroviral therapies are very effective in preventing HIV transmission. In most cases, the virus is under control within 6 months of a person starting this treatment.

Once the viral load — the amount of the virus present in the blood — is undetectable, there is virtually no risk of the virus transmitting to other people through blood, semen, or other bodily fluids.

In comparison with other fluids, blood contains the highest concentrations of HIV. The virus dies quickly when it leaves the body, so the risk of contracting HIV from contact with dried blood is low.

In a medical setting, a person could contract HIV if they get a cut from a blade or needle that has been in contact with blood that contains HIV.

However, the risk of contracting HIV in this way is very low.

The risk of contracting HIV from sharing equipment to inject drugs is very high because a person could inject blood that contains HIV directly into the bloodstream. The virus can survive for longer inside a syringe than when it is exposed to air.

According to the Centers for Disease Control and Prevention (CDC), there is a 1 in 160 chance of contracting HIV from using a needle that a person with HIV has used.

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Semen is the bodily fluid that contains the second highest concentration of HIV.

According to the HIV charity Avert, it is not possible for a person to get HIV by coming into contact with a condom containing the sperm of a person with the virus. The speed at which HIV dies outside a human host makes this impossible.

While HIV can spread via vaginal fluids, the virus tends to exist in smaller concentrations than it does in blood and semen.

It is not clear why this is the case, but it appears that hormones and the types of cells in the genital tract may play a role.

Breast milk contains HIV in lower concentrations than blood or semen.

A baby can contract HIV through breast milk, so the CDC recommend that people with HIV do not breastfeed, regardless of antiretroviral therapy or viral load.

HIV can also transmit to a baby through pregnancy or birth. However, this is becoming less common with recent developments in care.

If a person with HIV is receiving effective antiretroviral therapy, and they give HIV medicine to the baby for 4–6 weeks after delivery, the risk of the baby contracting HIV can be less than 1%.

The most common ways people contract HIV in the United States are through sharing equipment when injecting drugs and having anal or vaginal sex without barrier contraceptives. Anal sex poses a higher risk than vaginal sex, as there is a greater chance of tissue damage.

Although it is less common, HIV may pass to an infant during pregnancy, birth, or breastfeeding.

In extremely rare cases, HIV may spread if blood comes into contact with an open wound. There is a chance of this occurring if partners engage in open-mouth kissing, and both have bleeding gums or open sores within the mouth.

However, saliva that does not contain blood cannot transmit HIV. People cannot get HIV from closed-mouth or cheek kissing.

People can reduce or eliminate the chance of contracting HIV by using barrier contraceptives or taking preventive HIV therapy, known as pre-exposure prophylaxis (PrEP).

PrEP is a pill that a person can take once a day to minimize the chance of contracting HIV. It may be helpful for those who:

  • have a partner with HIV
  • have a partner with an unknown HIV status
  • have multiple partners
  • share needles to inject drugs

Read more about HIV transmission here.

It is not possible to contract HIV from the following:

  • mosquito and tick bites
  • sexual activities that do not involve the exchange of bodily fluids, such as mutual masturbation
  • contact with the saliva, tears, or sweat of a person with HIV
  • hugging, cheek kissing, or shaking hands with someone with HIV
  • sharing toilets or cutlery

Many myths and much misinformation surrounds the transmission of HIV. Read more here.

HIV cannot survive for long outside the human body, which means that the risk of contracting HIV from dried blood or semen is low.

If a person suspects that they have come into contact with HIV in the last 72 hours, they can use an emergency prevention method called post-exposure prophylaxis (PEP).

Find out how to undergo testing for HIV in the U.S. here.

Although inequities exist between different regions and populations, modern antiretroviral therapy has made it possible for people with HIV to live long, healthy lives without the virus transmitting to others.