What is influenza?

Influenza is a contagious respiratory illness caused by a virus that infects the nose, throat and the lungs. Some may experience mild to severe illness; influenza may lead to death in some cases. The influenza vaccine is the best protection against the illness.

An infected person may infect another beginning 1 day before symptoms develop or up to 5 to 7 days after becoming infected. The influenza virus is spread through the air via coughs or sneezes within short distances. Additionally, patients may become infected with influenza by touching a surface or object that has the influenza virus on it and then touching their own mouth, eyes or nose.

Influenza is diagnosed by testing the throat, sputum or nose. Rapid tests are currently available; however, it is important to know that people may be infected with influenza even when results are negative.
Signs and symptoms of influenza include:

Fever or feeling feverish/chills;
Cough;
Sore throat;
Runny/stuffy nose;
Muscle/body aches;
Headaches;
Fatigue.

Vomiting and diarrhea also may occur, although they are most common among children.
Complications from influenza include viral pneumonia, secondary bacterial pneumonia, sinus infections and the worsening of pre-existing health conditions.

Between 3 million and 5 million cases of severe influenza occur each year in outbreaks around the world, which lead to between 250,000 and 500,000 deaths. Death from influenza is most common among young children, the elderly and those with pre-existing conditions. Although pandemics are less frequent, during the 20th century, three influenza pandemics occurred: Spanish influenza during 1918, Asian influenza during 1958 and Hong Kong influenza in 1968 — each pandemic resulted in more than 1 million deaths.

Additional information may be found at these websites:

http://www.cdc.gov/flu/keyfacts.htm

http://www.who.int/topics/influenza/en/

http://en.wikipedia.org/wiki/Influenza