The chance of contracting HIV from a single episode of high-risk sex can be estimated based on appropriate information, but only estimates are available, and there are no particularly precise statistics. On average, about 1 in 1000 people are infected during a single episode of high-risk sex. However, if the sexual intercourse lasts for a longer period of time, the probability of infection may increase. If there is a break in the skin or mucous membrane or a wound during the process, exposure to the body fluids of a person with AIDS will also significantly increase the probability of infection. A period of time after such a situation occurs can be tested for AIDS antibodies to determine if you are infected.