Shaykh al-Albānī said, speaking about fearing someone on the basis of mere suspicion of illness:

I know many doctors who do not shake hands with people fearing that there might be an infectious microbe in the hand of this person. For this reason, they do not shake hands with people and this is a waswasah (whispering)… the [occurrence of the] whisper [is thought by people to be] restricted to some of the worshippers, but it has passed on to those, to other than the worshippers, to the doctors and their likes… So the meaning [here] is that this is a whispering (waswasah) which destroys personal ties and human relations which are established between people. The foundation is that every person’s leftovers and interaction with them is that he is upon fiṭrah (original disposition) and upon health and wellbeing. Thus, when it is established that Zayd from among the people he has, by way of example—Allāh forbid—the disease of tuberculosis and drinks from a vessel, then you can keep away from this, but you should have certain knowledge that he is afflicted with the disease of tuberculosis. As for a whisper, maybe he has it, maybe has it, then this is not permissible, because this is having an evil opinion about your Muslim brother and secondly it comprises cutting of ties of brotherhood between you and your Muslim brother. As for when it is verifiably established that he is afflicted [with the disease], then you can take precautions and avoid drinking [from the same vessel] and shaking his hand. And this is not from the whisper (waswasah) and nor absence of reliance upon Allāh as is claimed by some people.

Abu Iyaad