Is my DS at risk from my nieces warts?

[VikingEmma]

My 8 year old niece has warts on her fingers and now in and around her nostrils from picking her nose! My DS is only 6 weeks old and I'm concerned that shes going to infect him. We're going to stay with my parents and my niece will also be there which means she'll be touching a lot of stuff that I will also touch, putting me at risk and in turn my DS. Not to mention her touching him!

Would it be unreasonable of me to stop her from touching him? And how do I go about telling her or my sister without causing offence?

ooh, that's a tricky one.
I don't think YABU, but I can also say from experience that they don't necessarily spread all that easily. At least, I've been in households where one person had them but no one else got them.