How long is the window period for HIV infection?

Q: Somebody pricked my girlfriend with an infected needle 4 months back, we do not know whether the needle was infected or not. We have got ourselves tested and we have been tested negative for HIV a week back. Taking the window period into consideration, is she safe now or do we still have to wait and get her tested after sometime? Is it safe to have sex now after 4 months? If I have sex with her now and she tests positive later, will I be infected by the virus? How long is the window period usually?

A:The window period is usually about 3 months but can be upto 6 months. The period to wait to be sure is therefore about 6 months. Now that you have both tested negative at 4 months you can decide if you want to wait or prefer to go ahead but with a condom. Remember however that the condom isnot 100% safe as accidents can and do happen. If you have unprotected sex with a person in the window period you have a chance of getting infected.