Is it better not to go to the mosque when sick (e.g., with a cold) for fear of harming other worshippers, even if it is permissible to go for Friday prayer?

Friday and congregational prayers are obligatory for an able man, and it is not permissible to miss them except for an excuse.

The illnesses mentioned in the question are not considered valid excuses for missing Friday and congregational prayers, unless the patient is harmed by them and finds it impossible to go to the mosque, in which case he is permitted to miss them.

Some jurists have stipulated that for leprosy to be a valid excuse, it must be severe and cause harm to people.