What is high risk exposure? Any exposure where there is reasonably high possibility of HIV transmission from an infected individual to a person at risk of infection is called as a high risk exposure. If someone has unprotected sex, with an unknown partner or a commercial sex worker, or with a partner he or she solicits on the internet , these are when one of the partner is HIV infected and the sexual act was unprotected there is a chance of transmission other forms of high risk exposure are someone which has multiple sex partner, that increases the risks of HIV transmission. Other forms of high risk exposures are for example injection needle use and sharing of these needles. One other forms of high risk exposure is a clinical exposure, that is working in hospital or a place where someone could be infected and if one is exposed through a needle s tick injury or a splash of blood in one’s eyes or other mucus membranes, all this constitutes to high risk exposure. The things you have to keep in mind is this is not only about HIV but also about Hepatitis B or Hepatitis C or syphilis or few other conditions where the exposed individual is at risk, the window period refers to that period after an exposure the infection has happened but the test is unable to detect and classically the antibody test or the ELISA is unable to detect the fact that the infection has already occurred. In the past with 3rd generation ELISA test, this period used to be as long as 3 months. Today with the availability of PCR tests it can be as short as 15 days, the 4th generation antigen antibody tests the window period associated with that is typically less than a month. Can the window period be extended? No matter what tests you use as long as the tests you use is a reliable tests from a reliable lab, if the exposure happens from a lab and the tests are negative then you can be assure that your HIV status is negative.