AIDS cannot be ruled out after 3 weeks of high-risk behavior; it usually takes 6 weeks to rule it out. From the time of infection with HIV (human immunodeficiency virus) to the development of AIDS, there are three periods: acute HIV infection, asymptomatic HIV infection and AIDS. In the acute HIV infection stage, there is a period of time in which the corresponding antibodies cannot be detected, which is called the “window period”, and the window period of the third-generation testing technology currently used in most hospitals is around 2-6 weeks, so it cannot be ruled out in 3 weeks. It is recommended to take the test after 6 weeks of high-risk behavior, and if the result is negative, the test can be repeated in 3-6 months to rule out the case of a longer window period. There is currently no cure for AIDS, avoiding high-risk behavior and establishing healthy sexual attitudes is the key to preventing AIDS. If you find that there is a possibility of infection, you should immediately go to the hospital for examination and take blocking drugs.