Hello, and thank you for your medical question on e Health Forum.
Every act of unprotected sex - does not lead to HIV infection.
First, the chances that the concerned partner was indeed HIV positive is a point to be determined.
The risk of HIV infection is high with unprotected intercourse with partner of unknown HIV status, risky sexual behavior, multiple sexual partners, IV drug use, and association with other STDs.
Risk of acquring HIV are as follows:
A. Female-to-male transmission is 0.04% per act and
B. Male-to-female transmission is 0.08% per act.
C. The rate for receptive anal intercourse is much higher, 1.7% per act
The need for HIV testing depends on how high risk does the person has for HIV infection. If the risk is very high, then testing for HIV is advisable.
HIV is diagnosed based on the serological detection in the blood samples.
A person after exposure to HIV can get tested as early as 4 weeks to 12 weeks with the ELISA for HIV antibody test.
If a test is done at 12 weeks after exposure, and it is negative and there is no need to repeat the test again.
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