After the occurrence of high-risk sexual behavior, if infected with HIV, usually 2-6 weeks after the occurrence of sexual behavior, at this time there will be a transient flu-like symptoms, such as fever, sore throat, joint pain, rash, lymph nodes, liver and spleen enlargement, etc., the above clinical manifestations last for 1-2 weeks can disappear on their own. During this period of time, HIV antibody cannot be detected by blood test, and HIV antibody can remain negative for 2-3 months, and a few patients can delay up to 6 months, which is called the window period. If there is impure sex, it is recommended that blood tests be taken at a regular hospital 3 months after the occurrence of the test. If it is negative, it needs to be checked again after 3 months. If both results are negative, it is considered unlikely to be infected with HIV.