I scoured and couldnt find one doorknob or door handle story of one actual door being attributed to a cold or flu.
Must not be true.
I’m glad, b117, that you could find no attribution, but the risk remains viable.
RB, since hand to mouth transmission is more to the common cold, one would suspect doorknobs or handles being a pretty good source of transmission even if it hasn’t been studied directly. Transmission of the flu seems primarily airborne although hand to nose contact can do it as well.
Motto: It’s good to wash one’s hands often.
Good Day to You Both.