Meet the H1N1 virus

 
    
Recent electron microscope images of the H1N1 virus from the Centre for Disease Control & Prevention (CDC), Atlanta
Taken from their website: CDC 
 
This is how the new H1N1 flu virus looks like, its cell size about 80 – 120 nanometers in diameter (ref: ICTVdb database).  1 nanometer (nm) = 10-9 m or one millionth of a millimeter.  The above samples were taken from an infected patient in California and photographed on April 27th 2009 at the CDC in Atlanta, Georgia. 
 
The drawing below shows a model of the influenza A virus and a description of its structure.  Diagram and explanation of how the virus infects its host, is taken from the Suburban Emergency Management Project (SEMP) which is a global knowledge-based organisation focused on community-based disaster management (website link: SEMP)
 
For those who are not from the life sciences or medical field, the following description might not be easy to follow.
 
HA – Hemagglutinin; NA – Neuraminidase (these are the little pin-like objects on the viral surface)

What is the function of HA and NA viral surface projections anyway? The function of the HA protein is to bind virus particles to susceptible cells in the host animal. The function of the NA protein is mainly at the end of the life cycle of the virus at which time it facilitates the release of the virus particles from the infected cell surfaces during the budding processes. The HA and NA proteins are the antigens against which neutralizing antibodies are directed by the host animal’s immune defense system.

 
Diagram above: Model of the influenza A virus showing HA and NA receptors projecting from the surface of the virus.
 
The diagram below explains how the flu virus could mutate when it is passed from one species to another, with the pig as the host in which the different influenza strains mix and undergo genetic reassortment to form new and dangerous strains.
 

An influenza virus can be passed from one species (e.g., birds) through an intermediate animal host (e.g., pigs) to a third species (e.g., humans). Pigs have been proposed to the “mixing vessel” for the generation of reassortment influenza A viruses between humans and birds because—and this is very important—pigs can easily support replication of both avian and human influenza A viruses within their cells.

 

 

    

Transmission of the influenza virus through species.

Source: Carolyn Buxton Bridges, MD, Influenza Branch, Division of Viral and Rickettsial Diseases,

Centers for Disease Control and Prevention, Atlanta, Georgia: “Human influenza viruses and the potential for inter-species transmission”

 
  
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