Being sick doesn't mean you can actually miss a court date just because you're sick.
If you're actually in the hospital and can have the hospital prove you're in the hospital or prove you were in the hospital during the court date then that would get you out of trouble for missing court.
But just because you have the flu or cold virus doesn't mean you can miss court.
If you do have the flu or cold you should still appear and if they notice that you're sick then they may decide to have you go home and appear at a later date.
But sometimes you may just go through the court process and get the court over with.
It depends on what you're going to court for.
But if you just call in sick to court then they will still likely issue a bench warrant for your arrest.
So if possible just appear in court and get it over with even though it can be hard to appear in court with the cold or flu.