High-risk sex is one of the ways of HIV transmission. The chance of HIV infection is related to the number of high-risk sex, viral load and immunity, and medication. 1. Number of high-risk sex: The chance of HIV infection is relatively low when one high-risk sex occurs. The probability of HIV transmission from male to female is about 0.1%-0.2%, and the probability of transmission from female to male is less than 0.1%. The longer and more the number of high-risk sex, the more the risk will be superimposed, leading to a higher chance of HIV infection; 2. Viral load and immunity: the lower the immune function of the infected person, the higher the chance of being infected; at the same time, the higher the viral load of the patient, the greater the chance of infection to the other person; 3. Medication taking: when high-risk sex occurs, take AIDS blocking drugs as soon as possible within 24 hours The earlier you take the medication, the lower the chance of infection. In addition, other ways of HIV transmission include blood transmission, such as importation of blood products of unknown origin, medical occupational exposure, etc. The chance of infection is relatively high, the chance of infection by blood transfusion is 92.5%, and the chance of infection by percutaneous needle stick is 0.3%.