How quickly does it take for aids to spread in your body after having sex?

New HIV infection: Hiv can simmer in the immune system for a few days after infection but by day 14 to day 21 it will have begun spreading widely via the blood circulation system. Remember that in any exposure one has a window of 72 hours to act to prevent the infection. Post exposure prophylaxis in initiated by putting one on HIV medications for one month. This can cut the chance of infection significantly.