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当伊波拉病毒来袭 九死一生

kira86 于2009-02-24发布 l 已有人浏览
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A Doctor Who Left His Mark on a World That Lives in Fear of Ebola迅雷专用 This is the VOA Special English Deve
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A Doctor Who Left His Mark on a World That Lives in Fear of Ebola


迅雷专用

This is the VOA Special English Development Report.

伊波拉病毒(Ebola virus)可说是人类病毒中最凶残的杀手。它除了有极高的致死率(可高达90%),感染者会遭受到极度的生理痛苦(例如:高烧、喉咙痛、肌肉疼痛、呕吐、腹泻、精神异常),患者的死状也极为恐怖(牙龈出血、眼鼻流出血水、血便、出血不止、内脏器官溃烂),因此伊波拉病毒所引起的病徵就被称为「伊波拉出血热」(Ebola hemorrhagic fever)〔注一〕。而到目前为止,科学家仍然没有对付伊波拉病毒有效的药物治疗及疫苗预防方法。

在以前的科普小说,例如《第四级病毒》(Level 4: Virus Hunters of the CDC)、《伊波拉浩劫》(The Hot Zone,又译《棘手地带》)以及《伊波拉病毒》(Ebola: a Documentary Novel of its First Explosion),还有电影「危机总动员」(Outbreak)〔注二〕等,就是以这个杀人如麻的病毒作为题材。

1976年,伊波拉病毒首次在非洲现身,科学家却一直不知道它的传染窝(reservoir)究竟是何种动物。换句话说,伊波拉病毒到底从何而来,科学家还是一头雾水。到2005年12月,一个由非洲及欧洲多国联合组成的研究团队,终于证实蝙蝠是伊波拉病毒的传染窝。

从2001~2005年间,位于非洲西部的加彭(Gabonese Republic)及刚果共和国(The Republic of Congo)爆发多起人类感染伊波拉病毒的疫情,同时当地亦出现大猩猩及黑猩猩(非洲人猿)感染伊波拉病毒的情况。因此,为了找出伊波拉病毒的传染窝,研究人员总共捕捉超过1000头动物,当中包括蝙蝠六百多隻、雀鸟两百多隻、小型嵴椎动物一百多头。最后,在部分的锤头果蝠(Hypsignathus monstrosus)、富氏前肩头果蝠(Epomops franqueti)与小项圈果蝠(Myonycteris torquata)的血清中发现伊波拉病毒的抗体。而在这些健康蝙蝠的肝脏及脾脏中,还找到伊波拉病毒的遗传物质,肝脏及脾脏正是伊波拉病毒的首要感染器官。

以上三种果蝠的地理分布范围都是在非洲西部大西洋海岸及中部内陆地带,正好都是伊波拉病毒曾经肆虐的地区。将这些果蝠中找到的伊波拉病毒基因序列,与感染人类的伊波拉病毒基因序列进一步分析比对,发现它们与伊波拉病毒中最强悍的萨伊株(Zaire strain)属同一群。以上发现也符合多年前的研究:以人为方式让蝙蝠感染伊波拉病毒后,病毒能顺利地在蝙蝠体内複製,但是蝙蝠却不会生病。
在乾燥的季节中,猿类动物比较容易感染伊波拉病毒。这时,正好是森林中果实不足的日子,到处觅食的果蝠与其他动物争取食物时,就容易互相接触。蝙蝠在饥饿或怀孕的特殊生理情况下,本身的免疫能力会有所改变,除了蝙蝠变得较有攻击性之外,也可能有利于伊波拉病毒在蝙蝠体内複製增生,以致猩猩更容易受感染,而爆发伊波拉疫症。当我们知道伊波拉病毒的传染窝是蝙蝠后,公卫人员就可以教育当地民众,儘量避免接触及捕捉这些果蝠作为食用。

除了伊波拉病毒,蝙蝠也是其他多种病毒的传染窝,包括:狂犬病毒(rabies virus)、拉萨病毒(lyssavirus)、圣路易脑炎病毒(St. Louis encephalitis virus)、亨德拉病毒(Hendra virus)、立百病毒(Nipah virus)以及SARS冠状病毒〔注三〕。蝙蝠真可说是「恶贯满盈」。

那麽,为什麽蝙蝠能有这种能耐,可以与多种致命的病毒共存而不生病呢?目前我们已知蝙蝠是长寿的哺乳类动物,而哺乳类动物骨头裡的骨髓负责生产免疫系统的 B细胞,但由于蝙蝠能飞,其骨骼与鸟类一样是中空的,那麽蝙蝠有B细胞吗?由于我们对蝙蝠的生理及免疫系统所知有限,目前还不能解答这些问题。但是,相信以上发现将会加速科学家对蝙蝠的生理学研究,也希望从这当中得到如何对付这些病毒的启示。

Health officials in the Democratic Republic of Congo have declared the end of an outbreak of Ebola virus. Cases were first identified in December in the southern province of Kasai Occidental. The World Health Organization says officials reported a total of thirty-two cases, including fifteen deaths.

The worst form of the disease kills nine out of ten victims. Ebola is a hemorrhagic fever. It causes unstoppable bleeding. It spreads through contact with blood and other bodily fluids. There are no cures, but researchers continue to learn more about how the feared virus works.

It was named for the Ebola River in the former Zaire, now the Democratic Republic of Congo. A doctor in Zaire, Ngoy Mushola, documented the first outbreak in nineteen seventy- six. Hundreds of people were infected, and most died.

The epidemic might have been even worse had it not been for the father of the actress Glenn Close.

Doctor William Close, an American, worked in Zaire for sixteen years. For a time he was one of only three doctors, and the only surgeon, at a huge hospital in Kinshasa. Later he was the administrator. He was also chief doctor of Zaire's army and personal physician to President Mobutu Sese Seko.

One night, Doctor Close was on a plane, returning from a visit to the United States. He heard two other passengers talking about the epidemic. The United States Centers for Disease Control had sent them to help.

One was a virus expert. Karl Johnson had identified and photographed the Ebola virus just days earlier. The other was Joel Breman, another C.D.C. expert. Doctor Close spent the flight talking with them.

Then, in Zaire, he quickly used his connections and influence with the government. Doctor Breman remembers how William Close's planning and administration helped the medical team end the epidemic. He organized supply flights, for example, to affected areas.

To contain the spread of the virus, people were restricted to villages. Medical workers were given protective clothing. Equipment was carefully disinfected.

After his work in Africa, William Close returned to the United States. He became a country doctor, as he had always wanted. He was still working in Big Piney, Wyoming, when he died of a heart attack on January fifteenth. He was eighty-four years old. Joel Breman says, "Doctor Close left his mark on the world."

And that's the VOA Special English Development Report, written by Jerilyn Watson. I'm Steve Ember.

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