When I am the baal korei people often shake my hand after aliyot . I am sure that not all of them wash negel vaaser. Must I wash my hands after touching their hands before mussaf? (There is no rabbi speech I can do it then)
Does the halacha change if there is only 10 men in the room?
Thank you for your question.
You do not have to wash your hands after touching their hand. Although there may be a preference to do so, there is no obligation on you to do that.
The halacha will not change if there are only ten men in the room.
Kapei Aharon (Vol. 2 E:H siman 8 pg. 87 D:H Umnum also quoted in Daas Noteh vol 1 ftnt. 320), where he writes that we don’t find that a person who d=touches something that has ruach ra that he has to wash his hands. For example, a person who touches the hand of a person who is sleeping, or a person who touches food that was left underneath a bed, that he has to wash his hands. Additionally, this idea is not brought in the Shulchan Aruch, not in the majority of the poskim. Nevertheless, there are poskim who do say to wash your hands, see Ben Ish Chai Toldos 12, and quoted in Kaf Hachayim 4-17. Also see Piskei Teshuvos 4-11, that although it is not required there is a preference to do so if it isn’t difficult.