In the fall of 1917, a new strain of influenza swirled around the globe. At first, it resembled a typical flu epidemic: Most deaths occurred among the elderly, while younger people recovered quickly. However, in the summer of 1918, a deadlier version of the same virus began spreading, with disastrous consequence. In total, the pandemic killed at least 50 million people — about 3 percent of the world’s population at the time. That two-wave pattern is typical of pandemic flu viruses, which is why many scientists worry that the 2009 H1N1 (“swine”) flu virus might evolve into a deadlier form. H1N1, first reported in March 2009 in Mexico, contains a mix of human, swine and avian flu genes, which prompted fears that it could prove deadlier than typical seasonal flu viruses. However, the death toll was much lower than initially feared, in large part because the virus turned out to be relatively inefficient at spreading from person to person. In a new study from MIT, researchers have identified a single mutation in the H1N1 genetic makeup that would allow it to be much more easily transmitted between people. The finding, reported in the March 2 edition of the journal Public Library of Science (PLoS) One, should give the World Health Organization, which tracks influenza evolution, something to watch out for, says Ram Sasisekharan, senior author of the paper. “There is a constant need to monitor the evolution of these viruses,” says Sasisekharan, the Edward Hood Taplin Professor and director of the Harvard-MIT Division of Health Sciences and Technology. Some new H1N1 strains have already emerged, and the key question, Sasisekharan adds, is whether those strains will have greater ability to infect humans. –Physics.org

1917年的秋天，一种新的流感病毒在全球各地盘旋。起初，它类似于典型的流行流感：大多数死亡发生在老年人，而年轻人很快恢复。

然而，1918年开始，一个病毒的同版本开始致命蔓延，在夏天造成了灾难性后果。

总体而言，杀人流感造成至少5000万人，世界上当时大约3成的人口死亡。

这两个波模式是典型的流感病毒，这就是为什么许多科学家担心，2009年H1N1流感（“猪”）流感病毒可能演变成致命形势的典型。

H1N1病毒，首先是在2009年3月在墨西哥报道，包含了人类，猪和禽流感的基因，这让人们担心它相比一般季节性流感病毒，是更加致命的组合。然而，死亡人数远低于最初的担心，在很大程度上是因为病毒在人与人之间传播竟然是相对低效的。

在麻省理工学院新的研究中，研究人员已经发现了H1N1病毒基因结构中的单个突变，使其能够更加容易在人与人之间传播。

这一发现，在3月2日科学公共图书馆杂志（公共科学图书馆）一版刊登发表。

论文的资深作者，Ram Sasisekharan说，应该让世界卫生组织，追踪流感的演变，需要注意这些东西。

“有必要不断监测这些病毒的演变”爱德华胡德塔普林教授，以及卫生科学与技术，哈佛麻省理工部主任Sasisekharan说。

一些新的H1N1病毒菌种已经出现，Sasisekharan补充道，关键问题是，这些病毒菌种是否将有更大的能力来感染人类。
                                   ---- Physics.org

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