The rate of HIV transmission through percutaneous inoculation (i.e., a needle or other instrument that pierces the skin) is 0.3%.
Splashes of infectious material to mucous membranes (e.g., conjunctivae or oral mucosa) or broken skin may transmit HIV infection in 0.09% of the cases.
The per-contact risk of HIV transmission from sexual exposure varies according to the nature of the exposure:
- 1-30% with receptive anal intercourse
- 0.1-10.0% with insertive anal intercourse and receptive vaginal intercourse
- 0.1-1.0% with insertive vaginal intercourse
Oral intercourse is considered to pose a lower risk of HIV transmission but there are case reports of HIV infections in persons in whom the only reported risk factor was oral intercourse.
The risk of transmission associated with sharing needles for injection-drug use is 0.67% per needle-sharing contact.
Postexposure Prophylaxis for HIV Infection. Raphael J. Landovitz, M.D., and Judith S. Currier, M.D. NEJM, Volume 361:1768-1775 October 29, 2009 Number 18.
Image source: Diagram of HIV. Image source: Wikipedia.