Tópico: Novas linhagens do vírus da gripe aviária identificadas

[Buckaroo Banzai]

Bird Flu Genome Study Shows New Strains, Western Spread

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Their study of 36 genomes of the virus collected from wild birds in Europe, the Middle East and Africa (EMA), and Vietnam confirms not only that the virus has very recently spread west from Asia, but that two of the new western strains have already independently combined, or reassorted, to create a new strain.

Several samples also contained the mutation associated with the form of the "bird flu" that caused several human deaths in 2006. It is the virus's ability to rapidly mutate into a pathogen that may eventually be passed between humans that concerns health officials about a worldwide pandemic of H5N1 influenza.

The study also produced some evidence that strengthens the case that humans have had an impact on the movement of the flu out of Asia .

"This is the first time anyone's looked at all of the H5N1 genomes in the west," said Steven Salzberg, the study's lead author and director of the University of Maryland Center for Bioinformatics and Computational Biology. "Until now, the studies have been primarily on samples from the Far East . Our study shows that the virus is spreading west, and that there have been three separate introductions of H5N1 in Europe, the Middle East and Africa."

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The broad dispersal of the different forms of the virus throughout the different countries over a relatively short period of time points to the possibility of human movement, rather than wild birds as the reason for the quick spread of the H5N1. "The migratory pathways of wild birds don't correspond with the movement of the genomes that we sequenced," said Salzberg. "Humans carry chickens between many of the countries in our study, often transporting them across great distances. That and the weak biosecurity standards in most rural areas point to human-related movement of live poultry as the source of the introduction of H5N1 in some countries."

While the study "dramatically increased the number of genomes that have been sequenced, we have to do more surveys," Salzberg said. "It's surprising that we found what we did with such a small sample."

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http://www.sciencedaily.com/releases/2007/04/070418211906.htm