Influenza, commonly known as "the flu", is an infectious disease caused by an influenza virus. Symptoms can be mild to severe. The most common symptoms include: high fever, runny nose, sore throat, muscle and joint pain, headache, coughing, and feeling tired. The flu attacks the lungs, nose and throat. Young children, older adults, pregnant women and people with chronic disease or weak immune systems are at high risk. Symptoms include fever, chills, muscle aches, cough, congestion, runny nose, headaches and fatigue. Flu is primarily treated with rest and fluid intake to allow the body to fight the infection on its own. Paracetamol may help cure the symptoms but NSAIDs should be avoided. An annual vaccine can help prevent the flu and limit its complications.