When you have the flu virus you should not really drive because when you have the flu your reaction times are slower and you're not thinking clearly.
You're also fatigued and so may not be able to react to situations in a timely manner on the road and may cause a car crash or get into a car crash.
I've driven home from work before when I got the flu and needed to go home after I went to work with the flu and thought I would be okay but then decided that I needed to go home.
I drove home and was really tired and nearly crashed the car into another one in front of me because I was fatigued and had a headache and not feeling very good at all.
After that I always stayed home from work when I have the flu and never drove with the flu.
It's best to stay home and rest and not risk your life or others around you when you have the flu.
Maybe just driving around the block in town would be okay but not on the highway such as if you need to run to the store to get some medicine or something and the store is in the same town where you can drive slower then it might be okay.
But stay off the highways when you have the flu to avoid a crash.