作者:Emma Hitt, PhD
出處:WebMD醫學新聞
May 22, 2009 — 根據分析50個新型A型H1N1流感病毒株樣本的分析,新型A型H1N1流感病毒基因圖的基因已經循環一段時間而未被發現。
根據今日登載於科學期刊的此一報告,存在許多現象,包括在亞洲或美國的基因重新排列組合,這些事件造成新型A型(H1N1)病毒的起源。
作者們寫道,何處最容易發生基因重新排列組合依舊不清楚;該報告由墨西哥、英國與美國的科學家共同合作完成。
資深作者、疾病控制與預防中心(CDC)國家免疫與呼吸道疾病中心、流感小組主任Nancy Cox博士今天也在記者會中討論這個發現。
Cox博士表示,該研究再度強調豬隻是重要流感病毒宿主的這個事實,可能會造成人類嚴重的呼吸道疾病爆發,甚至大流行。本研究的結果顯示,全球都需要對豬隻的流感病毒採取更全面的監控。
研究者對獲自墨西哥和美國的病毒進行全部或部份的基因圖序列。新病毒株的8個流感基因片段之前都未曾在人類或豬病毒中出現。
根據該報告,所有片段都起源於鳥類宿主,且之後在1918至1998年間的各種時間進入豬隻。這8個基因片段中,6個被視為來自三重重組的豬病毒,包括了人類、豬與鳥類的DNA,自1998年開始循環。其他2個片段來自歐亞豬病毒,之前未曾在歐亞之外發現。
根據報導本報告的新聞稿,這一系列的基因片段並未出現在其他A型流感病毒中已經發現的高傳染性或致病性特徵,認為有其他尚未知的序列與病毒複製及在人類擴散有關。
本報告也發現,根據在紅血球凝集素蛋白質的改變,新病毒株可能有不同於季節性人類流感的抗原性性質,但是類似那些其他源自豬隻的A型流感(H1N1)病毒。
CDC今天報告指出,美國有6,552例可能與確認H1N1案例,但他們估計,約有100,000人可能感染H1N1病毒。總共有9例死亡與超過300例住院。CDC發言人表示,目前,全國約有60所學校關閉,共約42,000名學童停課。
Report Describes Origins of Influenza A (1 H1N1) Virus
By Emma Hitt, PhD
Medscape Medical News
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. |