The influenza virus causes a broad spectrum of clinical illness that varies in severity and duration amongst different individuals. Influenza infection has many of the same symptoms as the common cold (sore throat, cough, runny nose), but the systemic symptoms (fever, chills, muscle aches) are classically more abrupt and severe. A small percent of individuals do not experience the classic high fever, severe muscle aches, and fatigue.
Flu Symptoms(most experience some or all of these symptoms):
Diarrhea and vomiting (infrequent – mainly in young children and the elderly).
• Acute onset of Fever ( ≥ 100.0) and Cough/Sore Throat has a positive predictive value (79%-88%) for the flu when influenza is confirmed to be circulating in the community.
• Young children and older persons (> 60 yrs) are less likely to experience typical influenza signs and symptoms (e.g., fever and cough). Mild illness without fever was reported in 6%–33% of persons infected with 2009 H1N1 virus.
• Among those who had serologic evidence of 2009 H1N1 virus infection, 36% did not shed detectable virus or report illness.