How Long Can HIV Live Outside of the Body?

Comparing Theoretical Risk and Documented Risk

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Thomas Marthinsen

HIV has created such an intense fear of infection in some that it extends well beyond the fear of sexual transmission. In fact, some people remain convinced that you can get HIV by coming into contact with an object or surface on which there may be HIV-infected blood or semen.

After all, it would seem reasonable to suggest that the more blood or semen there is, the longer the virus can survive outside of the body.

And, in turn, if the virus is able to survive, it surely has the potential to infect, right?

Assessing the Risk

Given these parameters, it would fair to say that, yes, there is a chance of survival, albeit limited. Under specific conditions, HIV can survive outside of the body for hours or even days if the temperature, humidity, UV exposure, and pH balance are all just right. It is a very unusual set of conditions but one that is, in fact, possible.

But, does that necessarily mean that a person who touches or otherwise comes into casual contact with HIV-infected blood on semen run the risk of infection?

The answer to that question is almost universally "no." To understand why this is, you would need to differentiate between what is a perceived risk and a documented risk.

Perceived and Documented HIV Risk

A perceived (or theoretical) risk is one that is based on belief rather than fact and persists despite the unlikeliness of the event ever occurring.

By contrast, a documented (or actual) risk is based on statistical evidence of something actually occurring. Where a perceived risk is about theory, a documented risk is about fact.

With regards to HIV, the potential to infect does not translate into an actual risk unless the exposure satisfies four specific conditions:

  1. There must be body fluids in which HIV can thrive. This includes semen, blood, vaginal fluid, and breast milk. HIV cannot thrive in parts of the body that have high acidity (such as the stomach or bladder).
  2. There must be a route by which HIV can enter the body. This includes sexual intercourse, shared needles, occupational exposure, or transmission from mother to child.
  3. The virus must be able to reach vulnerable cells inside of the body. This requires the rupture or deep penetration of the skin and/or the absorption of the virus through the mucosal tissues of the vagina or anus. Scrapes, abrasions, and skin prick do not offer the deep penetration needed for an infection to occur. HIV cannot pass through intact skin.
  4. There must be sufficient quantities of virus in the body fluids. Saliva, sweat, and tears all either contain enzymes the inhibit HIV or have a pH hostile to HIV.

Unless all of these conditions are satisfied, an HIV infection simply cannot occur.

Conditions by Which HIV Can Survive

If HIV were to survive outside of the body for more than a few minutes, it could only do so under these specific environmental conditions:

  • Colder temperatures below 39 degrees Fahrenheit are considered ideal for HIV to thrive. By contrast, HIV does not do well at room temperature (68 degrees Fahrenheit) and continues to decline as it reaches and exceeds body temperature (98.6 degrees Fahrenheit).
  • The ideal pH level for HIV is between 7.0 and 8.0, with the optimal pH of 7.1. Anything above or below these levels is considered unsuitable for survival.
  • HIV can survive in dried blood at room temperature for up to six days, although the concentrations of virus in dried blood will invariably be low to negligible.
  • HIV survives longer when is not exposed to ultraviolet (UV) radiation. UV light quickly degrades viral DNA as well as the lipids that make up the virus' shell, rendering it incapable of attaching to and infecting other cells.

Even given these parameters, there has yet to be a documented case of infection by means of a discarded syringe in a public place.

In 2008, the largest retrospective study of 274 Canadian children showed not one case of HIV following an injury with a discarded needle.

Moreover, in 2015, the Centers for Disease Control and Prevention could only confirm one infection by means of a needlestick injury since 1999, and that case involved a lab researcher who was working with a live HIV culture.

Similarly, there has never been a documented case of anyone ever being infected by spitting or by getting body fluids in the eyes from a person with HIV.

If You Have Been Exposed to HIV

Clearly, there is no way say how much body fluid or how big a wound is needed for an HIV infection to take place. If in doubt, always err on the side of caution and go to your nearest emergency room or walk-in clinic.

You can a be prescribed a 28-day course of oral medications, known as HIV post-exposure prophylaxis (PEP), which may avert an infection if treatment started within 24 to 48 hours of an exposure.

However, if you are having on-going or irrational fears about HIV, consider meeting with an HIV specialist, psychologist, or trained counselor. This is especially true if the fears are interfering with your relationships or quality of life. There are treatments available to help control these anxieties and improve your overall sense of wellbeing.

Sources:

Centers for Disease Control and Prevention. "Notes from the Field: Occupationally Acquired HIV Infection Among Health Care Workers United States, 1985-2013." MMWR. 2015; 63(53):1245-46.

Papenburg, J; Blais, D.; Moore, D.; et al. "Pediatric Injuries From Needles Discarded in the Community: Epidemiology and Risk of Seroconversion." Pediatrics. 2008; 122:e487-e492. DOI: 10.1542/peds.2008-0290.