I'm, uh... [Boy it seems like there are a few layers of misunderstanding here. Apparently Papyrus has come to the conclusion that Ginko... has no prior medical training and now is suddenly a doctor? He can work on correcting that a bit at a time later he guesses.]

Just the food, then. Right. ...Can't blame you for being worried, though. [His mouth twists for a moment as he thinks about what to say here.] Y'know, since you only ate the food, you should be alright by now - which means samples from you would be a big help in understanding how this might have affected your brother.