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Influenza (or as it is commonly known, the flu or the grippe) is a contagious disease caused by an RNA virus of the orthomyxoviridae family. It rapidly spreads around the world in seasonal epidemics, imposing considerable economic burden in the form of health care costs and lost productivity. Major genetic changes in the virus have caused three flu pandemics in the 20th century, killing many millions of people. The name comes from the old medical belief in unfavourable astrological influences as the cause of the disease.

Flu Symptoms

The virus attacks the respiratory tract, is transmitted from person to person by saliva droplets expelled by coughing, and causes the following symptoms of the flu:

  • Fever
  • Headache
  • Tiredness (can be extreme)
  • Dry cough
  • Sore throat
  • Nasal congestion
  • Sneezing
  • Irritated eyes
  • Body aches
  • Extreme coldness

Flu's effects are much more severe and last longer than those of the cold. Recovery takes about one to two weeks. Flu symptoms can be deadly, especially for the weak, old or chronically ill. Some flu pandemics have killed millions of people.

Most people who get the flu will recover in one to two weeks, but others will develop life-threatening complications (such as pneumonia). Millions of people in the United States (about 10% to 20% of U.S. residents) are infected with influenza each year. An average of about 36,000 people per year in the United States die from influenza, and 114,000 per year are admitted to a hospital as a result of influenza. Even healthy people can be affected, and serious problems from influenza can happen at any age. People age 65 years and older, people of any age with chronic medical conditions, and very young children are more likely to get complications from influenza. Pneumonia, bronchitis, sinus, and ear infections are four examples of such complications.

Symptoms of the flu 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.


It is possible to get vaccinated against influenza, however, due to the high mutability of the virus a particular flu vaccine formulation usually only works for about a year. The World Health Organization co-ordinates the contents of the vaccine each year to contain the most likely strains of the virus to attack the next year. The flu vaccine is usually recommended for anyone in a high-risk group who would be likely to suffer complications from influenza.

Posted by Staff at May 12, 2005 12:48 AM

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