Q: My girlfriend currently has mono and I have already had it. Is it OK if we have sex? What are any risks associated with having sex with her while she has mono?
A: Great question. Seems simple, but really lots of layers.
“Mono” (infectious mononucleosis) technically refers to a syndrome of symptoms – swollen lymph nodes, fever, sore throat, fatigue, etc. – rather than a specific infection. Most cases of mono in the US are thought to be caused by the Epstein-Barr virus (EBV) but other viruses, such as Cytomegalovirus, can cause mono as well. But let’s assume that we’re talking about the usual EBV version of mono.
If your girlfriend has typical symptoms and a blood test that confirmed the diagnosis, then she is almost certainly infectious. EBV concentrates in saliva, so people usually catch it through a cough, sharing utensils, or most famously, kissing. EBV can be transmitted in other ways. Although not technically considered a sexually transmitted infection, one published study suggests that EBV can be transmitted through sexual intercourse and that condoms offer some protection.
Most (not all) healthy people who have had EBV mono develop immunity to it and do not get sick from subsequent exposures, so there is little risk of you getting mono again if you guys have sex. You will almost assuredly be exposed to your girlfriend’s EBV – so there is a significant risk that you will be re-infected, but miniscule risk that you will develop mono again.
But let’s think about your girlfriend for a second. Assuming she actually feels up to having sex, is it safe for her?
It’s unlikely that having sex would pose any particular risks. Mono will sometimes cause a person’s spleen to become enlarged, however, which places them at risk of having a spleen rupture, a true surgical emergency. In fact, we often tell people with mono to avoid contact sports and certain other physical activities for several weeks to make sure the spleen has had time to return to normal size. So theoretically, depending on the vigorousness of the sex, there might be a risk of injury to your girlfriend’s spleen.
The severity of EBV mono can range from unnoticeable to severe (sometimes requiring hospitalization), with most people falling somewhere in the middle. I have no idea where along this spectrum your girlfriend falls, but if she was feeling lousy enough to end up in the doctor’s office, maybe sex isn’t really a priority for her at the moment? Why don’t you pick up some popsicles for her or offer to take her dog for a walk and reassess the sex thing in a day or two… or ten.
James R. Jacobs, M.D., Ph.D.
Student Health Services
The Ohio State University