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HIV and AIDS

Risk of Transmission Following Unprotected Sex

03/06/2006

Question:

I am a male and had unprotected sexual intercourse with my girlfriend sometime in December. She was on her first day of her menstruation. After hearing stories on HIV, I asked that she be checked using the ELFA method in February 2006 (about two months after our encounter) and I myself was checked for HIV 1 and 2 on February 15, 2006. Both of our results came out negative. And if I can recall, I believe I had myself checked around 10 weeks after our encounter last December.

May I know my risks, knowing that she tested negative 8 weeks after our last encounter and that I had a negative result after 10 weeks? Thank you.

Answer:

After being infected with Human Immunodeficiency Virus (HIV), a person develops antibody to the virus.  The test used to determine if a person has been infected with HIV is a test for the presence of antibody.  Therefore, if a person has become infected, but has not yet developed antibody, they will test negative but still be able to transmit the virus to others.  The delay between acquiring HIV infection and developing antibody (and thus a positive blood test) can be several weeks to several months.  Most people develop antibody within 6 weeks, but there may be a delay up to 3 months before antibody develops.

I cannot answer your question in detail because I don't know your complete medical and risk history, nor do I know it for your girlfriend.  You may want to discuss this with your doctor.  I am concerned that you are using "after the fact" testing to determine whether you or your partner are "safe".  Because of the delay between infection and the positive test, this is a risky strategy.

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Response by:

Peter T Frame, MD Peter T Frame, MD
Emeritus Professor of Clinical Medicine
College of Medicine
University of Cincinnati