A cold and the flu can sometimes be difficult to tell apart.
Dr. Marc Itskowitz, an internist at Allegheny General Hospital, said the flu comes on hard and fast.
"People describe it like getting hit by a truck. You just have no energy. You really can't get out of bed in the morning," Itskowitz said.
The flu also brings more serious body and muscle aches, Itskowitz said. Doctors said extreme exhaustion is another sign of the flu.
"A cold is usually more mild nasal congestion and runny nose. Those patients can usually go to work," Itskowitz said.
Itskowitz said if the flu is caught in its early stages there are some things doctors can do.
"If we catch it within 48 hours there is an anti-viral medication that we can offer patients that decreases the duration in the symptoms," Itskowitz said.
There is really no medicine to shorten a cold, Itskowitz said, but decongestants and other medicines can help with specific symptoms.