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Risk of HIV infection

The risk of HIV infection depends on many factors, the most important factors are:

  • type of exposure (needle, sexual intercourse, type of sexual intercourse)
  • presence of a Sexually Tranmitted Disease

Vaginal sex (for women) 0.1% chance of HIV infection. This may seem like a small chance but remember that you will probably have sex thousands of times in your life time. Also remember that this is a statistic. You may get HIV the first time that you have unprotected sex with an HIV partner but someone else may not get it for a lifetime of unprotected sex. Men have roughly half the chance of contracting HIV from vaginal sex from an infected partner than women, that is a 0.05% chance of contracting HIV.

For a man there is a 1 in 20 000 chance of contracting HIV from receiving oral sex. Needless to say, there are other undesirable infections that one can get from unprotected oral sex.

Mother to child transmission is 25% on childbirth without treatment, this can be reduced to 1 to 2 % if treatment is given.

Needle sharing has a 0.6% chance of infection according to Kaplan, E.H and Heimer, R. (1995) Intravenous drug users sometimes share needles back and forth on a repeated basis, this will increase the chances of infection. You can check if a loved one is using illegal drugs in the privacy of your own home. Click here for more information

Anal Sex (receiving) has a 0.5% chance of infection. This means that if you have unprotected anal sex 200 times with an HIV positive person, then statistically you will have been infected by HIV. This figure is according to Varghese, B., Maher, J.E., Peterman, T.A., Branson,B.M. And Steketee, R.W. (2002) “Reducing the risk of sexual HIV transmission: quantifying the per-act risk of HIV on the basis of choice of partner, sex act and condom use.” The reason that anal sex is more risky than vaginal sex is because the anal wall is not as thick as the vaginal wall and is more likely to tear.

It is worth remembering that the chances above increase dramatically if one or both partners have a sexually transmitted disease.