Which is the dangerous bird flu virus strain, and why?

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Main Category: Bird Flu / Avian Flu
Also Included In: Flu / Cold / SARS
Article Date: 29 Oct 2005 - 0:00 PDT

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All flu viruses are divided into three groups - A, B and C. Humans tend to get flu from types A and B. Type A only can cause pandemic.

The influenza viruses type A are made up of 16 H subtypes and 9 N subtypes. The H subtypes are epidemiologically the most important. They govern the ability of the virus to bind to and enter cells, where multiplication of the virus then occurs

The only subtypes known to cause pandemics are the H5 and H7. Not all the H5 and H7 subtypes cause severe disease in poultry (not all are highly pathogenic).

The N subtypes govern the release of newly formed virus from the cells.

When H5 and H7 viruses are allowed to circulate in poultry populations they can sometimes mutate into highly pathogenic forms. This has happened and a highly pathogenic (deadly) strain called H5N1 has emerged. This bird flu strain is highly contagious (among birds) and kills most of the birds it infects.

The dangerous bird flu strain is called H5N1. If this strain evolves (mutates) by exchanging genes with a normal flu virus that commonly infects humans, it could learn to spread among humans as easily as it spreads among birds. The mutated H5N1 virus strain would be much more deadly than any flu virus humans experience today.

Synopsys:

-- 3 Groups of Flu Viruses - A, B and C
--Type A only can cause pandemics.
--Type A made up of 16 H and 9 N subtypes
--Subtype H epidiomologically the most important
--Only H5 and H7 (not all) can cause severe disease in birds
--H5 and H7 if allowed to linger in flocks can mutate
--H5N1 is current deadly bird flu strain
--If H5N1 mutates, humans have a serious problem worldwide

Written by: Christian Nordqvist
Editor: Medical News Today
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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