Influenza is a contagious respiratory illness caused by influenza types A or B viruses. Influenza viruses are easily spread by airborne respiratory droplets from person to person (often by sneezing or coughing).

Symptoms of infection include fever, muscle aches, headache, malaise (a general feeling of sickness), nonproductive cough, sore throat, and runny nose. Most people who get the flu will have mild illness, will not need medical care or antiviral drugs, and will recover in less than two weeks. Some people, however, are more likely to get flu complications that result in being hospitalized and occasionally result in death.

Pneumonia, bronchitis, sinus infections and ear infections are examples of flu-related complications. The flu also can make chronic health problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic congestive heart failure may have worsening of this condition that is triggered by the flu.

Children younger than 5 but especially children younger than 2 years of age, adult 65 years and older, pregnant women and individuals with various chronic medical conditions are at greatest for hospitalization and possibly death related to infection.

For a full list of conditions http://www.cdc.gov/flu/about/disease/high_risk.htm

Influenza viruses are constantly changing, so it is not unusual for new strains of influenza virus to emerge at any time of the year. This year’s influenza vaccines were made using the following strains: