Flu Symptoms (Influenza)

The flu is a contagious respiratory illness caused by influenza viruses. Symptoms usually come on suddenly and include fever, chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headache, and fatigue. Some people, especially children, may also experience vomiting or diarrhea.

Influenza spreads mainly through droplets when infected people cough, sneeze, or talk. Risk is higher in children under 5, adults over 65, pregnant women, people with chronic illnesses (such as heart, lung, or kidney disease), and those with weakened immune systems.

Seek urgent care if flu symptoms include difficulty breathing, chest pain, severe muscle pain, dehydration, dizziness, persistent high fever, or if symptoms improve and then return with worsening cough or fever. Antiviral medications are most effective when started within 48 hours of symptom onset.