HIV enters the body through mucosa covering the genitalia and then reaches the lymph nodes that are draining that area. Once its reaches the lymph nodes, it multiplies and gets released in blood circulation. This takes about 4-12 days after possible exposure.

So there is no test which can detect HIV immediately after exposure (within 4 days). The person has to wait at least for four days to get a test done (usually P24 antigen testing or PCR can detect).

After the HIV is released in the blood, the body immune system tries to fight against this virus and starts producing antibodies against it. This antibody production starts within 2-8 weeks (15 days to 2 months) of infection and they become detectable after 3 weeks to 12 weeks (21 days to 3 months).

So testing after 3 months after exposure should definitely come positive if infection has occurred. The most common test done is ELISA for HIV 1 and 2 antibodies. So, if someone has tested negative after 1 year of exposure, he is most unlikely to be HIV positive.

How to stop the spread of HIV?

Safe sexual practices have to followed. Usage of condom is must when the sexual history of the partner is unknown. Having other sexually transmitted diseases and practicing high risk sexual behavior increases the chance of acquiring HIV infection.

Edited by Dr Vaishalee Punj