01/01/2007Influenza A Viruses

Influenza A viruses cause seasonal endemics as they mutate in small ways from year to year.  Influenza A causes the “flu” which entails fever, muscle aches, cough and extreme tiredness.  In the US, 5-20% get the flu each year, 200,000 are hospitalized and 36,000 die.  The young and old and those with underlying medical illness are most susceptible to severe infection.

There have been three pandemics since the 1900’s.  A pandemic is a world-wide outbreak that occurs when a radically different virus suddenly emerges.  In 1918-1919 there was a pandemic influenza outbreak called the “Spanish Flu” which killed 40-100 million people.  Although not known at the time, the Spanish flu originated as a strain of the avian flu.

Many believe that we are now overdue for a pandemic.  A specific strain of avian influenza A. H5N1, has been thought as a candidate for causing a pandemic for years.  This is a virus that infects waterfowl (primarily ducks).  The virus is shed in the feces and can be passed to chickens and other poultry.  In parts of Asia, ducks, pigs and humans live in crowded conditions and the virus can jump species.  The avian flu virus has spread to more than 40 countries and killed hundreds of millions of birds.  One hundred sixty people in 10 countries have been infected so far, and half of those infected have died.  If the virus mutates to allow efficient human to human transfer, we could have a pandemic.

The United States Department of Health and Human Services announced this month that it is awarding over  $130 million in contracts to expedite the development of a vaccine against the H5N1 strain of avian flu.  There are also antiviral medications such as Oseltamivir (Tamiflu) which may be protective against the avian flu, should a pandemic occur.

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