The 76-year-old actor was admitted after spending days at his home trying to fight off the bug. He was found to be severely dehydrated and put on an IV line to administer fluids, reported Examiner online.
The star is expected to make a full recovery and was reportedly moved out of the Intensive Care Unit.
A spokesman for Reynolds said, "He is doing better. They are taking care of him and his moustache."
A flu bug has swept across the US in the past three weeks killing 500 people, 20 of them children.
Reynolds, best known for films 'Deliverance and Smokey' and 'The Bandit', had heart surgery in 2010. He earned a Golden Globe award along with an Oscar nomination for the critically-acclaimed film 'Boogie Nights'.