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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.[1][2]

A sub-type of influenza A is H1N1.

Epidemiology[edit | edit source]

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

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.[1]

See also[edit | edit source]

Learn more[edit | edit source]

References[edit | edit source]

  1. "Influenza (Seasonal)". World Health Organization. Retrieved Aug 25, 2018. 
  2. "Flu Symptoms & Complications | Seasonal Influenza (Flu) | CDC". Jun 5, 2018. Retrieved Aug 25, 2018. 
  3. "Influenza". Retrieved Aug 25, 2018. 

World Health Organization (WHO) - "A specialized agency of the United Nations that is concerned with public health. It was established on 7 April 1948, and is headquartered in Geneva, Switzerland. The WHO is a member of the United Nations Development Group. Its predecessor, the Health Organization, was an agency of the League of Nations." The International Statistical Classification of Diseases and Related Health Problems (ICD) is maintained by WHO. (Learn more:

The information provided at this site is not intended to diagnose or treat any illness.
From MEpedia, a crowd-sourced encyclopedia of ME and CFS science and history.