Fourteen people in China have been infected with avian influenza H7N9 virus, which has never been isolated from humans.
Ok IB students here is a classical and modern genetic topic! All influenza strains begin in birds. It is an 8 stranded RNA virus. The strands are linear RNAs that if two or more viral particles infect the same cell the new viral packages have the potential to ‘reassort’ the 8 RNA strands leading to a new strain of influenza. There are 3 major groupings [Genus] of influenza: A, B, C. The strain in Shanghai is the H7N9.
The H refers to a glycoprotein [a protein with sugars atatched to it] on the envelop [phospholipid bilayer] of the viral particle [not all viral particles have an envelop – influenza obviously do]. The Heamagluttinin glycoprotein does 2 things: 1) allows the viral particle to bind to sugars on the surface of your cells [usually lung when you breathe them in] and 2) stimulate fusion of YOUR cell membrane with the VIRAL envelope membrane allowing the viral particle to fuse and enter YOUR cell. There are 17 types of hemagglutinin known and each one has different affinities to different sugar combinations on your cells. Some strains infect birds, or pigs, or bats or other creatures because they have different sugars on their cells than we do. But the viruses mutate and evolve. Those able to infect new hosts have a selective advantage and are naturally selected.
The N refers to neuraminadase. This enzyme is needed for new viral particles to be released from the infected cell. The neuraminidase enzymatically breaks the attraction of NEW hemagglutinin molecules from the cells glycoproteins allowing the NEW viral particles to be released. There are obviously many neuraminidase enzymes – hence the N9 in this case.
I could continue with more interesting aspects of influenze but I might have my IB do a project on it. Obviously its a hot topic in Shanghai right now.
See on www.virology.ws