The girls are required to go for periodic AIDS and other STD checks. However, the window period (when AIDS infection cannot be detected) that has resulted in two Singaporeans catching AIDS from blood transfusions applies to these prostitutes too. You also have to realise that the popular girls fuck more than 7 or 8 customers a day. If you happen to dip your dick into a pussy that is still dripping with AIDS infected sperm, no sporadic health checks are going to save your life.