Influenza (also known as the flu) is a contagious respiratory illness caused by flu viruses. It can cause mild to severe illness, and at times can lead to death. The flu is different from a cold. The flu usually comes on suddenly and may include these symptoms:

• Fever (usually high)
• Headache
• Extreme tiredness
• Dry cough
• Sore throat
• Runny or stuffy nose
• Muscle aches
• Stomach symptoms, such as nausea, vomiting, and diarrhea, also can occur but are more common in children than adults