What is flu?
Flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. Flu viruses cause illness, hospital stays, and deaths in the United States each year.
How serious is flu?
Flu illness can vary from mild to severe. While flu can be serious even in kids who are healthy, it can be especially dangerous for young children and children of any age who have certain chronic health conditions. Children younger than 5 years old–especially those younger than 2–are at higher risk of developing serious flu-related complications. Children of any age with certain chronic health conditions like asthma and diabetes are also at higher risk.