Two months ago I went to South Africa to travel,the drunk after I had unprotected sex with a sex worker.The prostitute is very excited, but also put my penis bitten,Therewas a slight bleeding!!!!I heard that South Africa is the high incidence of AIDS in the country,I felt very fear.In 34 days after unprotected sexual intercourse,I went to the hospital for detection.The doctor asked me to conduct a joint detection of antigen and antibody(The 4th generation test),The result was negative.How does this result is 100% accurate???I would like to ask in the future can i need to test again???