The could have taken a blood sample but the doctor chose to have them have sex because he is obviously a shipper! x3 also, this is literally just fiction. It doesn't have to be realistic... You take the fun out of the manga if you just complain about how this doesn't make sense! >:c stop adding your realistic human knowledge into fuckn FICTION YAOIII
And. Btw I should have put a laughing crying emoji at the end so that I wouldn't come off as that rude. I do realize I probably hurt some feelings so I should have looked into that more. Sorry if I came off rude. I try my best to be nice to people who are kind as well but sometimes I let me emotions get in the way of that. I hope you understand, I apologize. :)
Don't get me wrong, I'm all about yaoi sex. But couldn't they have just taken a blood sample from him and used that to extract the cultivated virus? If it's in his semen, it's in his blood, so why jump straight to "have sex"? In fact, there's less of a chance of air interacting with a sterile blood sample than his semen up the uke's butt. And how does that doctor even know without testing it that the virus can be transmitted through sexual contact? Not all viruses can, just like not all viruses can be transmitted via saliva. And wouldn't the virus need time to incubate in his body before his semen could be used as treatment? Just... AHHHH!!! I have so many problems with the science in this manhwa!