health

The most reliable estimates for the risk of human immunodeficiency virus

(HIV) transmission after a single exposure are from occupational exposures involving health care workers (HCWs) studied prospectively after exposure.

Such studies have estimated that the risk of HIV infection after a single occupational percutaneous exposure to HIV-infected blood is approximately 0.3% and after a mucous membrane exposure 0.09%. The risk of transmission after skin exposures, while not precisely quantified, is believed to be even smaller. The risk of transmission after a nonoccupational exposure has been more difficult to estimate, due in part to difficulties in determining the time, source, nature, and frequency of exposures. However, available data suggest that the per-episode risk is within the same order of magnitude as that

associated with percutaneous exposure. It must be emphasized that these estimates are averages and may be affected by a variety of factors.

For example, a retrospective case–control study found that HCWs who

sustained a percutaneous exposure to HIV-infected blood were more likely to become infected if they were exposed to a larger quantity of blood (deep injury, device visibly contaminated with blood, or device previously placed in the patient's vein or artery). In addition, transmission of HIV also was associated with injuries in which the source patient was terminally ill with AIDS. Several risk factors for sexual transmission have been identified, including genital ulcer disease and other coexisting sexually transmitted diseases.