HIV cannot survive for very long outside of the body, and it cannot replicate without a human host. There is no single answer to the question of how long HIV can survive outside of the body, as it depends on the fluid the virus is present in.
Transmission can occur when these fluids come into contact with a mucous membrane, such as those inside the rectum, vagina, and mouth, and those on the penis.
This article explores the factors affecting the survival time of HIV outside of the body, as well as how HIV can and cannot spread.
There is no set time, but in certain conditions, the virus may survive for several weeks.
This is because many factors influence its survival, including:
- the type and amount of body fluid that the virus is in
- the temperature of the environment
- the acidity of the surrounding environment
- whether there is exposure to sunlight
- environmental humidity
Of all the body fluids that can transmit HIV, blood contains the highest concentrations of the virus.
HIV may survive in dried blood for up to 5–6 days at room temperature. It might survive even longer inside blood that is within a syringe, as it does not have exposure to air.
Other factors that can determine the exact survival time of HIV outside the body include the volume of blood in the syringe and the temperature of the surrounding environment.
According to Aidsmap, one study looked at over 800 syringes containing different amounts of blood and found that the virus was able to survive "after 11 days."
According to the San Francisco AIDS Foundation, semen contains the second highest concentration of HIV, with vaginal fluids containing even less.
Aidsmap note that studies attempting to culture HIV from semen samples have so far been unsuccessful. This indicates that both the quantity and survival rate of HIV in semen outside of the body are very low.
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. This is due to the speed at which HIV dies outside of a human host.
While vaginal fluids can transmit HIV, 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.
The San Francisco AIDS Foundation suggest that of all body fluids that carry the virus, breast milk contains the lowest concentration of HIV.
While a small amount is unlikely to transmit HIV to an adult, it may pose a risk to infants, who regularly drink lots of breast milk.
One of the most common causes of HIV transmission in the United States is having anal or vaginal sex without a condom.
Another common cause of HIV transmission is sharing needles or syringes.
Although less common, HIV may pass from mother to baby during pregnancy, birth, or breastfeeding. However, according to Avert, taking antiretroviral medications during pregnancy and while breastfeeding can almost eliminate that possibility.
In extremely rare cases, HIV may spread if blood comes into contact with an open wound. One way that this may occur is 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.
It is not possible to transmit or contract HIV from the following:
- mosquito and tick bites
- sexual activities that do not involve the exchange of body fluids, such as mutual masturbation
- the saliva, tears, or sweat of a person with HIV
- hugging, shaking hands with, or closed-mouth kissing a person with HIV
- sharing toilets or cutlery with a person who has HIV
- using public swimming baths
Although HIV can survive for a short time in fluids outside the body, Aidsmap say that there are no cases of a person contracting HIV after coming into contact with spillages of blood, semen, or other body fluids.
Certain activities can, however, increase a person's risk of contracting HIV. A person can significantly reduce this risk by practicing safe sex and avoiding sharing needles.