Thank you for your inquiry. From what we gather from the question, you were asking about the risk of HIV infection from urethra exposure to menstrual blood in an environment of no air exposure. From the information given, this scenario is determined to be High Risk (there is evidence of transmission through these activities and are the majority of cases of transmission).
The scenario mentioned above does meet the components of the transmission equation (image below). In order for HIV transmission to occur, HIV positive fluid (blood, semen, vaginal fluid, anal fluid, breastmilk) must have direct access to the bloodstream through a High, Low, or sometimes Negligible Risk activity. In this case, menstrual blood (a fluid potentially carrying HIV), had direct access to the bloodstream via the urethra during an unprotected sexual activity. Additionally, in this case, the activity describes close contact between the vagina and urethra, making transmission possible due to a lack of air exposure.
If this activity was performed sooner than 72 hours ago, please refer to a health care provider for post-exposure prophylaxis (PEP): https://www.catie.ca/fact-sheets/prevention/post-exposure-prophylaxis-pep.
Recommendation: Please refer to a health care provider for HIV testing and PEP (if it has not yet been 72 hours since the activity described).
AIDS Vancouver Helpline/Online, Nancy
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