No pantsus were drawn this day
However, after rewatching it for - uhm - research, I noticed that she unties the ribbon around her neck for "no reason". Since it was shown in a rather important way, I start to doubt that this scene had no meaning at all and when we consider what Ikoma did at the end I get the feeling that she's been bitten once (and healed similiar to how Ikoma got "healed") and this is somewhat of a "unleash the forbidden curse"-move. Maybe her brother is just as clever as Ikoma and knows more about the virus than most people and helped her in the past.
Ikoma didn't just strangle himself either, he had this weird collar around his neck before he did it too which I assumed was more or less the last resort after he failed to stop it in his arm and later his shoulder.
The virus is clearly still in his system, his hair color changed and you can still see the infected, blueish veins comming out of his heart. So maybe that collar will help him to do the same thing later?
I guess it's impossible to grasp what was going on right now, I'm already interested in the explanations or at least in more hints.