Symptoms

One to two days after being infected the patient becomes suddenly ill. Many patients can tell exactly when they first felt ill. Symptoms include:

• chills
• muscle ache
• headache
• runny or stuffy nose
• extreme fatigue
• cough
• fever (often higher in children)
• temperature rises rapidly to 38 to 40 degrees C

The flu doesn't usually cause nausea, vomiting, or diarrhoea - what some call the "stomach flu" is more often food poisoning or a gastrointestinal virus. Patients infected with an influenza virus may have symptoms for as little as 24 hours, or as long as two weeks. On average, the symptoms last 4 to 5 days. Even after recovery, flu victims often get easily fatigued and it takes them a while to feel normal again. Compared with other viral respiratory infections like common colds, influenza causes more severe complications such as pneumonia, particularly in children, elderly people and other vulnerable groups.