HIV can live outside of the body for as long as a few weeks, depending on the conditions. In most cases, though, the virus is inactive and unable to cause an infection within hours of being outside the body.

There are many myths and misconceptions about how long HIV lives and is infectious in the air or on a surface outside the body.

Unless the virus is kept under specific conditions, the true answer is not very long.

Although it causes a serious disease that can’t be cleared by the body, HIV is very fragile in the outside environment. It quickly gets damaged and becomes inactive, or “dies.” Once inactive, HIV can’t become active again, so it’s the same as if it’s dead.

HIV spreads when blood or certain bodily fluids that have high amounts of active virus (like semen, vaginal fluids, rectal fluids, or breast milk) are exposed to one’s bloodstream.

For a person to contract HIV, there must be enough active virus in the fluid that encounters the bloodstream. This can occur through:

  • a mucous membrane, or “moist skin,” such as in the mouth, rectum, penis, or vagina
  • a significant opening in the skin
  • injection

Transmission of the virus most often happens during anal or vaginal sex, but it can also occur by sharing needles.

Factors that affect the survival of HIV outside the body include:

  • Temperature. HIV stays alive and active when kept in the cold but is killed by heat.
  • Sunlight. Ultraviolet light in sunshine damages the virus, so it’s no longer able to reproduce.
  • Amount of virus in the fluid. Generally, the higher the level of HIV virus in the fluid, the longer it will take for all of it to become inactive.
  • Level of acidity. HIV survives best at a pH around 7 and becomes inactive when the environment is even just a little more or less acidic.
  • Environmental humidity. Drying will lower the viral concentration of active virus as well.

When any of these factors aren’t perfect for HIV in its environment, survival time of the virus goes down.

HIV can’t survive for long in the environment. When fluid leaves the body and is exposed to air, it begins to dry up. As drying occurs, the virus becomes damaged and can become inactive. Once inactive, HIV is “dead” and no longer infectious.

Some research show that, even at levels much higher than usually found in the bodily fluids and blood of people with HIV, 90 to 99 percent of the virus is inactive within hours of being exposed to air.

However, even though exposure to the environment can inactivate the virus, studies have found that active virus can be detected outside of the body for at least several days, even as the fluid dries.

So, can you get HIV from a surface, such as a toilet seat? In short, no. The amount of active virus that would be able to transmit an infection in this scenario is negligible. A case of transmission from a surface (such as a toilet seat) has never been reported.

There’s nothing special about semen (or vaginal fluids, rectal fluids, or breast milk) that protects HIV so it can survive longer outside the body. As soon as any of the fluids that contain HIV leave the body and are exposed to air, the fluid dries up and inactivation of the virus starts.

HIV in blood from something like a cut or nosebleed can be active for several days, even in dried blood. The amount of virus is small, though, and unable to easily transmit infection.

HIV survival time in fluid outside of the body can increase when a small amount is left in a syringe. After an injection in someone with high levels of HIV, enough blood stays in the syringe to transmit the virus. Since it’s inside a syringe, the blood isn’t as exposed to air as it is on other surfaces.

According to the Centers for Disease Control and Prevention (CDC), when the temperature and other conditions are just right, HIV can live as long as 42 days in a syringe, but this typically involves refrigeration.

HIV lives the longest in a syringe at room temperature, but can still live up to 7 days at higher temperatures.

One older study showed that after 1 to 2 hours in tap water, only 10 percent of the HIV virus was still active. After 8 hours, only 0.1 percent was active. This shows that HIV doesn’t survive long when exposed to water.

Except under very specific conditions, HIV stays active and is able to cause an infection for only a very short time once it leaves the body.

Because there’s so much misinformation about the risk of getting HIV through casual contact with infected fluids on surfaces or the air, the CDC states specifically that HIV can’t be transmitted by air or water, or by sitting on a toilet.

In fact, except for sharing needles and syringes, there’s never been a documented case of a person contracting HIV from casual contact with infected fluid on a surface in the environment.

Read this article in Spanish.