MEDICAL

Most genetic changes in the flu viruses human, pig, and bird are small and subtle point mutations in the virus’s RNA. Less common but more alarming are sudden, wholesale changes that replace entire genes and are more likely to circumvent the immune system. This process, called genetic shift, is exactly what is now occurring in North American pigs. Thus, the latest swine influenza virus is a curious hybrid: The genes that code for its coat proteins derive from classical swine influenza, but half of its internal genes have been snatched whole from avian and human viruses.

Most commonly, the virus swaps genes that code for its two surface proteins: hemagglutinin (HA) and neuraminidase (NA). Both proteins spike off the virus’s outer coat, and HA initiates infection when it binds to receptors on host cells. The immune system of the infected animal targets sites on these molecules. Therefore, a virus with a novel HA can escape preexisting immune defenses—hence the pig deaths. Influenza viruses are named after their HA and NA components, as in “H1N1” or “H3N2.” Both human and swine influenzas have been historically limited to only a few of these varieties. Birds, on the other hand, can be infected by every combination of the virus’s 15 HA genes and nine NA genes, forming a vast global reservoir of virus. And pigs have receptors for both human and bird flu virus, making them crock pots for new viral combinations.

This season’s variant is an H1N1 with the internal genes of an H3N2. Its HA gene, derived from the classical swine influenza virus, appears to be rapidly mutating. The amount of sequence divergence among certain 2001 isolates “is as much as the difference between classical H1N1 viruses isolated in the 1960s and those isolated in the early 1990s,” Webby reports. If enough point mutations accumulate, that HA molecule could become unrecognizable to the immune systems of both pigs and humans.

(Read More on Free Ebook at PDF Format)

Download Swine Flu Chasing the Fickle.pdf

Tags: avian and human viruses | Chasing the Fickle Swine Flu | circumvent the immune system | classical swine influenza | genetic shift | H1n1 | H3N2 | hemagglutinin | immune defenses | neuraminidase | Swine Flu | swine influenza virus | the flu viruses human

You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

DO YOU WANT PUBLISH THIS ARTICLE INTO YOUR SITE?

<h2>Swine Flu Chasing the Fickle</h2> <p style="text-align: justify;">Most genetic changes in the flu viruses human, pig, and bird are small and subtle point <a title="mutations" href="http://911medicalcare.com/medicalcare/mutations/">mutations</a> in the virus’s RNA. Less common but more alarming are sudden, wholesale changes that replace entire genes and are more likely to circumvent the immune system. This process, called genetic shift, is exactly what is now occurring in North American pigs. Thus, the latest swine influenza virus is a curious hybrid: The genes that code for its coat proteins derive from classical swine influenza, but half of its internal genes have been snatched whole from avian and human viruses.</p> <p style="text-align: justify;">Most commonly, the virus swaps genes that code for its two surface proteins: <a title="hemagglutinin" href="http://911medicalcare.com/medicalcare/hemagglutinin/">hemagglutinin</a> (HA) and <a title="neuraminidase" href="http://911medicalcare.com/medicalcare/neuraminidase/">neuraminidase</a> (NA). Both proteins spike off the virus’s outer coat, and HA initiates infection when it binds to receptors on host cells. The immune system of the infected animal targets sites on these molecules. Therefore, a virus with a novel HA can escape preexisting immune defenses—hence the pig deaths. Influenza viruses are named after their HA and NA components, as in “H1N1” or “H3N2.” Both human and swine influenzas have been historically limited to only a few of these varieties. Birds, on the other hand, can be infected by every combination of the virus’s 15 HA genes and nine NA genes, forming a vast global reservoir of virus. And pigs have receptors for both human and bird flu virus, making them crock pots for new viral combinations.</p> <p style="text-align: justify;">This season’s variant is an H1N1 with the internal genes of an H3N2. Its HA gene, derived from the classical swine influenza virus, appears to be rapidly mutating. The amount of sequence divergence among certain 2001 isolates “is as much as the difference between classical H1N1 viruses isolated in the 1960s and those isolated in the early 1990s,” Webby reports. If enough point mutations accumulate, that HA molecule could become unrecognizable to the immune systems of both pigs and humans.</p> <p style="text-align: justify;">(Read More on Free Ebook at PDF Format)</p> <p style="text-align: justify;"><a href="http://911medicalcare.com/pdf/swine-flu-chasing-the-fickle" target="_blank">Download</a> Swine Flu Chasing the Fickle.pdf</p> <p><a href="http://911medicalcare.com/wp-content/uploads/2009/07/swine-flu-chasing-the-fickle-image.jpg"><img class="alignnone size-full wp-image-893" title="swine flu chasing the fickle image" src="http://911medicalcare.com/wp-content/uploads/2009/07/swine-flu-chasing-the-fickle-image.jpg" alt="swine flu chasing the fickle image" width="350" height="350" /></a></p><br/><a href="http://www.socialmarker.com/?link=http://911medicalcare.com/swine-flu/swine-flu-chasing-the-fickle/&title=Swine+Flu+Chasing+the+Fickle&text=...&tags=" target="_blank"><img src= "http://www.socialmarker.com/bookmark.gif" border="0" /></a><noscript><a href="http://www.socialmarker.com" >Social Bookmarking</a></noscript> <p>The article <a href="http://911medicalcare.com/swine-flu/swine-flu-chasing-the-fickle/">Swine Flu Chasing the Fickle</a> is provided by <a href="http://911medicalcare.com" title="Manual Nurse and health Guidelines"> Manual Nurse and Health Guidelines</a>. The article from<a href="http://911medicalcare.com" title="Medical"> Medical</a> site is freely distributed for non-commercial purposes to include the source for the article and does not alter the content.</p>

*copy-paste the code above into your post blog

Top incoming search terms for this post

intitle:"swine flu" AND "name (required)" AND "powered by wordpress" - swine - chasing the swine flu - Chasing the fickle swine flu -



Recent searches: ekg emergency nursing emergency nursing emergency nursing emergency nursing sample cover letter for RN New graduate nurse application letter sample letter of recommendation for Physical thera school nurse resume sample letter of recommendation for nurse