Drying is probably the main reason the virus doesn't survive outside the body. But as I said at the outset, this fact doesn't matter one way or the other.
Hi Dr. Handsfield:
Thank you so much for your timely reply.
I am curious about one of my questions in my original email. Is it true the fluid containing the virus have to dry in order for the HIV virus to die?
Many thanks.
Welcome to the forum. I'll try to help settle your concerns: you are not at significant risk for HIV from these events. Congratulations for using safe sex during this sort of exposure.
The answer to the title of your question (HIV survival time outside the body) is irrelevant. Whether or not the virus survives, and how long, doesn't matter. The important issue is that nobody ever catches HIV by contact with potentially infected secretions outside the body. To put it another way, the answer to your closing question is yes: it is true that HIV is only transmitted sexually when a bare penis (no condom) is inside another person's vagina, rectum or, rarely, mouth.
HIV is not very easily transmitted. That's why even with completely unprotected vaginal intercourse, with ejaculation in the vagina, if one partner has HIV, the chance of transmission averages roughly once for every 1,000 to 2,000 exposures. Infection is transmitted only when lots of virus has direct access to susceptible cells, which are deep in the body or under the superfical layers of skin. Exposure to "just one virus" (or other small amounts) is rarely if ever sufficient. The amount of virus to which you could have been exposed through condom reversal is almost certainly too low for transmission to occur. So even if we accept your premise that your partner had HIV, there is no realistic chance you were infected.
And anyway, I don't accept that premise. I agree a woman with the sexual lifestyle you describe is at higher than average risk of HIV. Still, heterosexually transmitted HIV is less common (in the US and other industrialized countries) than media stories would make you think. I would be surprised if your partner has any more than a 1% chance of having HIV, and it's probably a lot lower than that.
On the basis of risk assessment alone, you don't need HIV testing. However, you would not have asked the question unless you were nervous, and I doubt my reassurance alone is going to convince you it isn't necessary. Anyway, everyone who is sexually active outside a mutually monogamous relationship should be tested for HIV from time to time, like once a year -- so if you have't been tested recently, this would be a good time, while it's on your mind. While you're at it, get tested for the common STDs as well (urine for gonorrhea and chlamydia, blood test for syphilis); those risks are a lot higher than for HIV in this situation.
The time to reliable HIV testing has been discussed innumerable times on this forum. Just scan any 10-15 threads at random; or use the search link and enter "window period" or "seroconversion". The quick answer is that you could have a single combo test (for both HIV antibody and p24 antigen) 4 weeks or more after exposure, or a stand-alone antibody test after 6-8 weeks. You can ignore the common advice you will find about waiting 3 months; it isn't necessary.
Don't lose any sleep as you wait to be tested. You can definitely expect a negative result.
Best wishes and happy new year-- HHH, MD