Hello, AIDS has a window period. It is impossible to find out the HIV in the body of HIV-infected people by doing AIDS examination during the window period. Scientific research shows that if the initial examination is done 2-4 weeks after high risk, and the result is negative after 4 weeks, the infection rate can be ruled out about 98%; After 8 weeks, the reexamination was negative, and the infection rate was 99.99%. Only about one in ten thousand people have a window period of eight weeks to three months. In order to rule out the possibility of 100% infection, it is best to make a final review after 3 months, and negative results can be completely ruled out. I hope my answer is helpful to you.