• What's My Risk of Getting Infected With HIV?
• There Are No Guarantees!
• What Do the Numbers Mean?
• What Activities Are Riskiest?
• What About Oral Sex?
• What Increases the Risk of HIV Infection?
• The Bottom Line
The only way to know for sure whether you have been infected is to get tested. You should wait for 2 or 3 months after a possible exposure. Then get an HIV blood test.
You might know that you were exposed to HIV by sharing needles, a work-related accident, or unsafe sexual activity. In these cases, talk to your doctor immediately. Ask whether you can use HIV treatments to prevent infection. Ask about "post-exposure prophylaxis."
For regular partners who were active in anal sex, the risk for transmission was 1 in 10. The risk for the insertive partner (the "top") is believed to be about 10 times less than for the receptive partner (the "bottom").
The risk of HIV infection during vaginal intercourse is believed to be much less. One estimate was 1 in 200,000 for transmission from infected women to men and 1 in 100,000 for transmission from infected men to women.
These calculations only give a general idea of risk. They can tell you which activities carry a higher or lower risk. They cannot tell you if you have been infected. If the risk is 1 in 100, for example, it doesn't mean that you can engage in that activity 99 times without any risk of becoming infected. You might become infected with HIV after a single exposure. That can happen the first time you engage in a risky activity.
The next greatest risk for HIV infection is from unprotected sexual intercourse. Receptive anal intercourse carries the highest risk. The lining of the rectum is very thin. It is damaged very easily during sexual activity. This makes it easier for HIV to enter the body.
Vaginal intercourse has the next highest risk. The lining of the vagina is stronger than in the rectum, but it can still be damaged by sexual activity. All it takes is a tiny scrape that can be too small to see. The risk of infection is increased if there is any inflammation or infection in the vagina.
There is some risk for the active partner in anal or vaginal sex. It's possible for HIV to enter the penis through any open sores, or through the moist lining of the opening of the penis.
• The risk of HIV infection through oral sex is extremely low. It is much lower than for other types of unprotected sexual activity. However, other diseases, such as syphilis, can be transmitted through oral sex.
Several other factors increase the risk of transmitting HIV, or becoming infected. These factors apply to just about every possible way HIV can be transmitted.
• When the HIV-infected person is in the "acute infection" phase, the amount of virus in their blood is very high. This increases the chance that they can pass on the infection. Unfortunately, almost no one knows when they are in this phase of HIV infection. There's no way to tell by looking at them.
• When either person has a weakened immune system. This could be because of a long-term illness or an active infection like a herpes outbreak, syphilis, or the flu.
• When either person has open sores that get exposed to infected fluids. These could be cold sores, genital herpes, mouth ulcers, syphilis sores, or other cuts or breaks in the skin.
• When there is blood present.