Richard Thomas was sentenced to five years in prison in the United Kingdom last week for raping a woman in Greater Manchester while she slept. The victim says she had taken a sleeping pill and awoke as he was raping her after having broken into her home. According to the prosecutor, “She froze and no words were exchanged. He pulled up his shorts and left.” Thomas, who was drunk and on a combination of ecstasy and cocaine at the time, claims he has no recollection of the rape but pleaded guilty nonetheless. Though the court proceedings were little more than a formality given his plea, the case is now making international news because the victim is HIV-positive, and Thomas is waiting to see if he contracted the virus during the assault.

Thomas admits that he knew the victim socially and says that, though he does not remember the assault, he knows her to be honest. He told the court, “[She] would not lie, she tells the truth. If she says I have done it, I have done it.” He says he knew she had medical issues but was not aware she was HIV-positive; he reportedly collapsed when police officers told him and he realized the risk to his own health.

The rape occurred on July 20, but Thomas is expected to get his first test results this week because he needed to wait until the end of the “window period”—the time between becoming infected with HIV and developing antibodies that can be detected by the test. According to the Centers for Disease Control and Prevention (CDC), most people develop antibodies within two to eight weeks (the average time is 25 days), but it can take longer. If his results come back negative, Thomas will likely be retested in a few more weeks just to make sure.

The likelihood that Thomas is infected with HIV from this one incident is actually quite small. The CDC estimates that an individual will contract HIV from insertive penile/vaginal intercourse with an infected partner about 6.5 times out of 10,000 incidents. (Receptive partners have a somewhat higher risk of 10 times per 10,000 incidents.) This already small risk goes down significantly—as much as 96 percent—if the infected individual is taking antiretroviral drugs. The news reports about this case have not said whether the victim was on medication, but it is likely she was, as she was aware of her HIV status.

This case flips the issue of sexual assault and HIV on its head—most of the time, the question asked after a sexual assault is if the victim will contract HIV from his or her assailant.

In a fact sheet on sexual assault and sexually transmitted diseases (STDs), the CDC attempts to reassure survivors that the chances of HIV transmission are particularly small in part because it is not as easily transmitted as other STDs. While chlamydia and gonorrhea, for example, can be transmitted through skin to skin contact, HIV—which is found in blood, semen, and vaginal fluids—needs to get into the bloodstream. During sexual activity, HIV is most likely transmitted when semen or vaginal fluids come in contact with microscopic breaks or rips in the delicate lining of the vagina, vulva, penis, or rectum.

The CDC explains that in consensual vaginal sex, a person who does not know their partner’s HIV status has about a 0.1 to 0.2 percent chance of contracting HIV. This number is slightly higher for receptive anal intercourse (about 0.3 to 0.5 percent) and substantially lower for oral sex, which carries almost no risk of transmitting HIV. This may be different for assault, however:

Specific circumstances of an assault (e.g., bleeding, which often accompanies trauma) might increase risk for HIV transmission in cases involving vaginal, anal, or oral penetration. Site of exposure to ejaculate, viral load in ejaculate, and the presence of an STD or genital lesions in the assailant or survivor also might increase the risk for HIV.

Survivors of sexual assault may opt to receive post-exposure prophylaxis (PEP), which involves taking two or three antiretroviral drugs for a period of 28 days. PEP has to be started within 72 hours of exposure. It has been shown to be effective in reducing the risk of acquiring HIV in health-care workers who are exposed to HIV-infected blood, usually through needle sticks. The CDC says this about PEP in its fact sheet:

Although a definitive statement of benefit cannot be made regarding PEP after sexual assault, the possibility of HIV exposure from the assault should be assessed at the time of the postassault examination. The possible benefit of PEP in preventing HIV infection also should be discussed with the assault survivor if the assault poses a risk for HIV exposure.

When deciding whether to recommend PEP, health-care providers should consider factors such as the behavior of the assailant, if known. For example, men who have sex with men and intravenous drug users are at higher risk of being infected with HIV than others. When information on the individual assailant can’t be determined, health-care providers are encouraged to assess the local epidemiology of HIV and AIDS. They also need to assess the nature of the attack, including whether and where the assailant ejaculated and if there was tearing of the victim’s vagina or anus.

Thomas’ attorney says Thomas has been worried about the HIV results since learning of his victim’s status, though she acknowledges, “It is his own fault, if he had not committed this offence he would not have placed himself in this position.”

The same cannot be said when victims of sexual assault await their test results. Perhaps this table-turning case will raise awareness of what women and men who survive rape go through even after the incident itself is over.