(CNN) – Winter is the season for flu and colds, and it can be difficult to tell them apart.
Both the flu and the common cold affect the respiratory tract, but are caused by different viruses.
Stronger viruses cause the flu, which if left unchecked can develop into other complications, such as pneumonia or bacterial infections, and may require hospitalization.
Flu symptoms are worse than those of the common cold, and include fever, body aches, extreme fatigue and an intense dry cough.
Common colds usually just come with a lot of congestion, including runny or stuffy noses.
Tests can be done in the first few days of an illness to determine whether or not it is the flu. Those who are uncertain can call their doctor.
Small children, people with compromised immune systems and the elderly are susceptible to flu complications.
Flu cases are on the rise. According to the Centers for Disease Control and Prevention, influenza has hit the south central and southeastern parts of the U.S. hard in the past few weeks, and other parts of the country are seeing outbreaks.
The best way to avoid the flu is to get a flu shot, and there's still time. The flu season usually lasts until late February or early March.