There's a saying amongst performers that you don't call in sick unless you're actually dead. As a result, people have arrived at the stage door in states of raging fever, or so weak they could hardly stand.
Theatre folklore is full of stories about "doctor theatre", the term used for the extraordinary effect which the requirements of performance can have on the symptoms of illness.
Opera singers have been known to break bones on stage, continue singing till the curtain fell, and only then to feel the pain of the injury.
Performers have even heard tragic news, such as the death of a child or husband, just before entering in a comic role and played a whole show effortlessly, before collapsing in tears on their final exit.
