Signs and Symptoms of the Flu
Influenza, commonly called the “flu”, is a respiratory infection that is different from the “common cold” or the “stomach flu” (NIAID 2011). Influenza is primarily characterized by inflammation of tissues that line the nasal cavity, throat, the inner surface of the eyelids (ie, conjunctiva), and the lungs (NIH 2012a; Kim 2011; Sanders 2011; Snelgrove 2011). Common clinical symptoms of influenza include a sudden onset of fever, fatigue, headache, and muscle aches (Shobugawa 2012). Although both the flu and the common cold are caused by a viral infection of the respiratory system, symptoms of the common cold rarely include severe fever, headaches, or extreme exhaustion (NIAID 2011). More information is available in the Common Cold protocol.