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Biology and Genetics - Influenza Virus

Seasonal outbreaks of flu and its health complications account for important losses in direct medical costs and productivity

Influenza is a common infectious disease which is widespread or epidemic between December and April.  It is caused by an RNA virus from the Orthomyxoviridae family which has three major types, called A, B and C. Type A influenza is the most common human infection. Globally, the World Health Organization (WHO) estimates there are 1 billion cases of flu, 3–5 million cases of severe illness and 300,000–500,000 deaths annually. In Canada, the best estimates are that between 1% and 10% of people will get influenza every year if they are unimmunized. Of those who are infected, it is expected that the virus and its complications will kill between 4,000 and 8,000 people. Influenza can cause a range of symptoms depending on the strain and severity of the virus.  Common symptoms include:

  • Headache;
  • Chills and cough;
  • Fever;
  • Loss of appetite;
  • Muscle aches and fatigue;
  • Running nose;
  • Sneezing;
  • Watery eyes;
  • Throat irritation

Age groups at elevated risk of death from influenza include the elderly, young children and people with pre-existing chronic conditions such as asthma, diabetes, or cancer. In addition to the use of effective hygiene protocols (hand-washing) and active surveillance of the virus, prevention of influenza focuses on the use of vaccines.  Because of a unique feature of the influenza virus called antigenic drift, a new the vaccine has to be developed every year. To do this effectively, the pharmaceutical companies producing the vaccine need to predict the exact nature of the influenza which will appear in next winter‘s flu season.  Influenza A also infects birds.  If the Avian flu virus mutates in birds and then successfully infects humans, there is the potential for a wide-spread pandemic. The Canadian government, in partnership with the WHO now has a pandemic preparedness programme for flu pandemic.

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Contributor: Jennifer Eyvindson; Fan Mo

Last Reviewed: June 2nd, 2010

 

Last reviewed: June 2, 2010



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