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Report Describes Origins of Influenza A (1 H1N1) Virus Print E-mail
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พฤหัสบดี, 28 พฤษภาคม 2009
May 22, 2009 — Genes included in the novel influenza A (H1N1) genome have been circulating undetected for an extended period, according to an analysis of 50 samples of the novel influenza A (H1N1) strain."Several scenarios exist, including reassortment in Asia or the Americas, for the events that have lead to the genesis of the novel A (H1N1) virus," according to the report, which was published today in Science. "Where the reassortment event(s) most likely happened is currently unclear," the authors write. The report was a collaborative effort between researchers in Mexico, the United Kingdom, and the United States.The senior author of the paper, Nancy Cox, PhD, chief of the Influenza Division at the Centers for Disease Control and Prevention (CDC) National Center for Immunization and Respiratory Diseases also discussed the findings at a media briefing today."This study reinforces the fact that swine are an important reservoir for influenza viruses with the potential to cause significant respiratory outbreaks or even a possible pandemic in humans," Dr. Cox said. "The results of this study show a global need for more systemic surveillance of influenza viruses in pigs," she said.The researchers sequenced full or partial genomes of isolates obtained in Mexico and the United States. Combinations of the 8 influenza gene segments in the novel strain had not been previously described in either human or swine viruses.According to the report, all segments had originated in avian hosts and had then entered into the swine population at various times from 1918 to 1998. Of the 8 gene segments, 6 are thought to have resulted from triple reassortant swine viruses and include DNA from human, swine, and avian sources that had been circulating since 1998. The other 2 segments were derived from Eurasian swine viruses and had not been detected previously outside Eurasia."The sequences for the gene segments did not reveal the signatures of high transmissibility or virulence that have been found in other influenza A viruses, suggesting that other, yet-unknown sequences are responsible for the new virus' ability to replicate and spread in humans," according to a news release describing the paper.It was also found, on the basis of changes in the hemagglutinin protein, that the new strain may have antigenic properties distinct from seasonal human influenza but similar to those of other swine-origin influenza A (H1N1) viruses.The CDC today is reporting 6552 probable and confirmed cases of H1N1 in the United States, although they are estimating that about 100,000 people probably have been infected with the H1N1 virus. A total of 9 fatalities and more than 300 hospitalizations have been reported. Currently, about 60 school closings are taking place around the country, with about 42,000 students out of school, a CDC spokesperson said.
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