When people are exposed to HIV-positive infectious bodily fluids either through skin puncture, contact with mucous membranes or contact with damaged skin they are at risk for acquiring HIV. Pooled estimates give a risk of transmission with puncture exposures of 0.3% and mucous membrane exposures 0.63%.
Some guidelines state that "feces, nasal secretions, saliva, sputum, sweat, tears, urine, and vomitus are not considered potentially infectious unless they are visibly bloody." Given the rare nature of these events, rigorous study of the protective abilities of antiretrovirals are limited but do suggest that taking antiretrovirals after exposure can prevent transmission. It is unknown if three medications are better than two.
The sooner after exposure that ART is started the better — the recommendation is up to a week after exposure
— but after what period they become ineffective is unknown. Recommended duration of treatment is 4 weeks, based on animal studies. Their recommended regimen is emtricitabine + tenofovir + raltegravir (an INSTI). The rationale for this regimen is that it is "tolerable, potent, and conveniently administered, and it has been associated with minimal drug interactions."
People who are exposed to HIV should have follow up HIV testing at 6, 12, and 24 weeks.
Adapted from Wikipedia, the free encyclopedia. Internet. Accessed on April 30, 2016.