There are a few thing to understand in this. The semen or the ejaculatory fluid contains the virus and is infectious. However, the risk of transmission depends on a number of things. The first and the foremost is the source of the semen or the ejaculatory fluid, the individual, whose semen it was, if that person is infected or not. If that person is uninfected or HIV negative, then the question of HIV infection does not arise at all. The second thing is which part of the body of the exposed person came in contact with the semen or the ejaculatory fluid. Some of the common parts of the body which can get affected are which come in contact especially the skin of the hands or the other parts of the body. If the skin is intact, that is there is no scratches or cuts or bruises or other injuries, the risk of transmission of HIV infections is nil even if the person whose semen it was might be HIV positive. Some of the other parts of the body which can get exposed are the mucous membrane, that is the conjunctiva of the eyes, the mouth, the throat or the mucous membrane of the vagina or the rectum. Now the risk of transmission is greatest is for the unprotected, that is without the condom for the receptor, that is the bottom partner, anal sex, they tend to be the highest. But the risk remains with another mucus membrane. If a person is HIV positive and if they are under treatment and their virus levels in the blood, which is typically measured by the viral load is typically undetectable while one cannot say that the semen cannot be completely negative of the virus. The risk of transmission comes down. So to conclude, first if there is any situation where you believe where you have been being exposed, the wise thing is to get yourself screened. Secondly, the risk of HIV transmission depends whether the source is HIV positive. Which part of the body has been exposed to this semen or the ejaculatory fluid or of there were any cuts or bruises on the skin or if you are engaged in unprotected anal, vaginal or oral sex.
