Improving medical students

Influenza Review

Posted by medliorator on September 8, 2009

A plain language review of the influenza virus by Joseph Albietz:

The influenza season in the Northern hemisphere usually runs from October through May, with a peak mid-February.  Every season in the US between 5-20% of the US population is infected by influenza, and while the majority of people recover well from an influenza infection, not everyone will.  Annually 200,000 people are hospitalized, and on average 36,000 will die either from influenza or its complications.

Influenza is an RNA virus encoded by just 11 genes on 8 separate RNA segments  …One in every 1000-10,000 nucleotides is mis-transcribed by influenza, giving it one of the highest mutation rates known… Two genes encode influenza’s characteristic surface proteins hemagglutinin (HA) and neuraminidase (NA).  There are 16 types of HA, 9 of NA, and respectively these two proteins serve to bind the virus to a target cell and to release new viral particles from a host cell, and they also happen to be the parts of influenza the immune system recognizes.  Every so often a transcription error will change the conformation of either HA or NA just enough so that it cannot be recognized by the immune system.

the 2009 (H1N1) is distinct from the seasonal A (H1N1).  It appears to be a “triple recombination,” with characteristics derived from human, bird, and swine influenzas.  When our population was tested for antibodies against 2009 (H1N1) nearly no children, and less than 10% of those under the age of 65 had reactive antibodies, and of those over 65 only 33% showed any response.  It seems no one has seen a similar influenza in half a century.  This means that the vast majority of our population is susceptible to infection this season

An Influenza Primer [Science-Based Medicine]

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