Influenza

Influenza, commonly known as "the flu", is an infectious disease caused by an influenza virus. There are four types of influenza virus, types A and B (seasonal), C which is less frequent causing mild infections and not a public health threat, and D which primarily affect cattle and not known to infect or cause illness in people.

Seasonal influenza is characterized by a sudden onset fever or feeling feverish/chills, a cough (usually dry), headache, muscle pain and joint pain, severe malaise (feeling unwell), fatigue, sore throat and runny or stuffy nose. Vomiting and diarrhea is more common in children than adults.

A sub-type of influenza A is H1N1.

Epidemiology
All age groups can be affected but there are groups that are at more risk than others.
 * children under 59 months
 * health care workers
 * elderly
 * pregnant women
 * individuals with chronic medical conditions


 * asthma
 * cardiac
 * diabetes
 * hematologic
 * liver
 * metabolic
 * neurodevelopment
 * pulmonary
 * renal

Influenza spreads easily with rapid transmission in crowded areas such as schools and nursing homes. Sneezing and coughing spreads droplets containing viruses which can spread over three feet. Persons within range can become infected by breathing in these droplets. The virus also spreads by hands contaminated with influenza. From time of infection to illness is about 2 days but can be one to four days.
 * individuals with immunosuppressive conditions
 * HIV/AIDS
 * malignancy
 * receiving chemotherapy or steroids

Learn more

 * Flu Symptoms - What are the emergency warning signs of flu sickness? (Adults, children, and infants.)
 * Influenza Video short
 * Influenza (Seasonal) Fact Sheet
 * Wikipedia