》存在亚洲的不是典型的流感 [王升/译]

欧洲的防治工作，图为英国专业人员的清扫养鸡场

禽流感病毒杂显微镜下的切片

禽流感的世界性分布和扩散及死亡地区

禽流感病毒如何传染给人体

在高倍显微镜下显示的禽流感病毒

西班牙的流感病毒在最近已从一些不知名的动物中进入到了人身上，它们正把这些无免疫力的灾民们留给这个新来的凶兆。
原因一你通常在几天的小病或感冒之后又恢复为流感，那是因为你的免疫系统已经识别了它<指病毒>，在此之前，<往往>不知道如何回答<这种症状>。今年的病毒将不是去年的复制品，因为这种病毒不断地突变着，而且它看起来完全相似，因而你的身体可能几乎保持在检查<出病毒为止的状态>中。
虽然，新种病毒是遵循着动物世界——一个广阔的A型流感病毒的禁区<活动范围>而来，偶而，那些<带病毒的>动物会引起人类最严重的疾病<瘟疫——意译为“灭顶之灾”>。经过大量的研究，在1960年至1970年末，从澳大利亚的大宝礁到加拿大北部地区的湖泊中，Rober Webster和他的同事们追踪流感，来到它们的发源地。“流感病毒从哪里来？”他问，“从野生鸟类世界，野生的水栖鸟类——水鸟，鸭子以及沿岸栖息的鸟类。”
一系列的流感病毒的亚种寄生在鸟类的内脏中，大多数病毒无害于鸟类自身或其它一些动物。但偶然，流感亦会传染给家里养的禽类。更难得<突如其来>的是，<假如>一只鸟的病毒或它的一些基因悄悄地进入到了带有A型流感病毒的无数水池中，就会传染给人类。一般<正常>情况，一种<禽>流感只会传染给鸟类，而无法攻击人类，因为它不具备入侵和在人体细胞中存活生长的能力。直到最近，科学家认为avain病毒能获得一种能力，就是只有通过交换使等量的病毒性基因沉溺其中。因为流感病毒携带它们的基因信息，大约有8个不连接的RNA断片，如果它们开始接触，那么不同的亚种很容易交换基因。其结果是，<这种病毒>进化成<具有新功能的>变异后代。

因为avain流感与人类的流感使之混淆了，他们只能传染同一类动物。科学家经过长期思考<深思熟虑/探索>，猪很有可能使血管混淆，因为猪的细胞有表层分子，因而允许两种病毒的进入<有允许两种病毒进入的表层分子>。一只猪可想而知，在同一个农场中，从农夫身上感染了人类的流感，以及从一只鸟和鸭子那里感染禽流感。这两种病毒能这时“reassort”，生产杂交——在最差的情况——它将能立即传染到人体的细胞上，而这时，仍携带禽流感的基因将使人体免疫系统彻底地患上这些新型的不寻常地恶性的流感。

Reassortmant说明了两个较轻度的20世纪，1957年——1968年间的流感大流行。在近每年的新型流感亚种<的调查>显示，在前几年的来自于鸟类病毒的新基因，已经引起了感情思想的爆发<人们的思想崩溃>，何况再结合来自于人类的流感病毒。这种新流行的病毒向全世界高速推进<大肆蔓延>，一共死去大约两百条生命<共计约两百万人一同归西>。

Taubenberger现在认为，当今所发生的事情不同于发生在1918年<的那次>。“我们认为那是相当有可能的，因为病毒并非源于先前地正传播于人类的流感病毒”，他说。所有的基因都介于传播于没有来自于人类的先天基因<无先天免疫的>的帮助的人们之中。

》LIVES IN ASIA IS NO ORDINARY FLU [转摘《NATIONAL GEOGRAPHIC》]

王升按——本文是《国家地理》英文版杂志有关禽流感的文章，只是选段。上面一篇是译文，我将翻译此杂志上有关禽流感的系列文章。
The Spanish flu virus had recently crossed into people from some unknown animal,leaving victims with little immunity to this new threat.

ONE REASON you generally get over the flu after a few day's discomfort is that your immune system has seen it before and knows how to respond.This year's bug won't be a carbon copy of last year's,because the virus mutates constantly.But it will look similar enough that your body can almost always keep it in check.

Every so often,though,something new comes along from that animal world——a vast preserve of type A flu viruses,the ones that cause the most serious illness in humans.In far-flung studies in the late 1960s and 1970s,from Australia's Great Barrier Reef to lakes in northern Canada,Rober Webster and his colleagues tracked flu to its source."Where do flu viruses come from?"he asks,"From the wild birds of the world,the wild aquatic birds—— the waterfowl,the ducks,the shorebirds."

Dozens of flu subtype iwhabit the birds' guts,mostly harmless to their hosts or to any other creature.But occasionally one infects domestic poultry.Even more rarely,a bird virus or some of its genes slip into the much smaller pool of type A viruses that infect humans.Normally a flu virus good at infecting birds can't attack humans because it isn't equipped to invade and grow in human cells.Until recently scientists thought avain viruses could gain that ability only by indulging in the viral equivalent of sex.Because flu viruses carry their genetic information on eight separate RNA segments,it's easy for different subtypes to swap genes if they happen to meet.The result——offspring with new abilities.

For an avain flu and human flu to mix it up, they have to infect the same animal. Scientists have long considered the pig a likely mixing vessel, because pig cells have surface molecules that allow entry to both kinds of virus. A pig could conceivably catch a human flu from a farmer and a bird virus from, say, ducks at the same farm. The two viruses could then "reassort", creating a hybrid that——in the worst case——would now be able to infect human cells while still carrying bird-virus genes that would make it radically new to the immune system of the people who catch it, and unusually virulent.

Reassortment explains the two lesser flu pandemics of the 20th century, in 1957 and 1968. In each year a new flu subtpye appeared, combining genes from the human virus that had been causing mind outbreaks in prior years with new genes from a bird virus. The new pandemic viruses raced around the world, together killing about two million people.

But in 1918, Taubenberger now believes, something different happened. "We think it's pretty likely that the virus was not derived from a previously cirulating human virus", he says. All of its genes make it as an animal virus, pure and simple, that some how crossed to people without the help of genes from a previous human strain.