Reply to an earlier Q regarding controller with a cold..
As well as being a distraction with his/her coughing and spluttering, you have to think about the possibility of infecting other controllers..
In an air conditioned room, the cold/flu bug can be very potent. It is better to be struggling, short of one controller on the monday, than to have 3 controllers catch the cold of him and all be ill at the same time 3 days later..
Usually, if he is suffering from runny nose/cough, then he will be unable to concentrate on his job, and is therefore a liability, as well as being infectious. When it dies down to blocked nose etc, it is usually no longer infectious and is not too much of a distraction to the person who has it.
In the military, controllers are treated medically the same as aircrew... would you want a pilot flying who was streaming snot out of his nose?!!