Sexual transmission is by far the most important means of HIV transmission, and unprotected sex in daily life has a higher chance of spreading HIV. When having unprotected vaginal sex with a person diagnosed with HIV, the chance of being infected is 0.08% if the woman is the healthy partner and 0.04% if the man is the healthy partner. Unprotected anal sex with a person diagnosed with HIV has a 0.11% chance of being infected for the active partner and a 1.38% chance for the passive partner. In the case of unprotected oral sex with a person diagnosed with AIDS, the probability of being infected is 0.01% if the recipient is healthy and 0.02% if the perpetrator is healthy. The above probabilities are theoretical; in real life, the presence of ulcers or sores on the genitals or skin or mucous membranes increases the chances of contracting AIDS by a factor of 20.