VOA慢速英语2021--蝙蝠和疫情爆发的源头

Scientists have long suspected that the rate of new infectious diseases could speed up. This is especially possible in developing countries where human and animal contact is increasing.

Changes in the environment are moving many species of animals into new living spaces.

Those movements, combined with more human contact with animals as people move deeper into forests, increases the chances of a virus jumping species.

Diseases that can jump from animals to humans are called zoonotic diseases. These diseases can be problematic because the human body is not designed to defend against this kind of invasion.

The host animal species often shows no signs of disease. This is because the animal's body has already learned to deal with the virus. However, when such viruses or other disease-causing microorganisms jump from animals to humans, the effects can be deadly.

Many scientists believe bats were the first carriers of the coronavirus that causes COVID-19. The animals have been linked to past outbreaks of coronaviruses in humans. Studies have shown that bats are natural hosts to many other viruses as well.

One example is the Ebola virus, which caused deadly outbreaks in Western Africa. The Nipah virus, also carried by bats, has caused human outbreaks across South and Southeast Asia. Health experts say Nipah is serious enough to possibly cause a "serious epidemic¹."

The coronavirus family of viruses also includes diseases such as Severe Acute Respiratory Syndrome² (SARS) and Middle East Respiratory Syndrome (MERS). Scientists have discovered that SARS and MERS were caused by viruses that started in bats, with other animals serving as intermediate hosts.

The only other animals coming close to hosting as many viruses as bats are rodents³. There are about 2,300 species of rodents, making up about 40 percent of all mammals. While rodents are believed to have more viruses as a group, bats host more viruses per species.

Scientists believe the many types of species in both groups can create more possibilities for viruses.

Some bats live in forests while others are found in caves. Most eat insects such as beetles⁴, moths⁵ and mosquitoes. Some bats eat fruit, nectar, seeds and pollen⁶ from flowers. Others eat small animals such as birds, fish, frogs and lizards⁷. A small number of bats feed on blood.

Bats also provide many benefits to the environment. Some bats play important parts in plant pollination⁸ and spreading seeds. Bats can pollinate more than 500 species of plants including avocados, bananas, dates and mangoes.

In Southeast Asia, durian, a highly valued fruit, can be effectively pollinated only by the Dawn Bat. In this way, bats are important economically for people.

Insect-eating bats also serve to naturally control insect populations. These bats eat millions of insects at night, including some that cause severe damage to crops.

Words in This Story

epidemic – n. an occurrence in which a disease spreads very quickly and affects a large number of people

host – n. a living organism on or in which a parasite⁹ lives

intermediate host – adj. a host which is normally used by a parasite in the course of its life cycle and in which it may multiply asexually but not sexually

mammals – n. a type of animal that feeds milk to its young and that usually has hair or fur covering most of its skin

pollen – n. the very fine usually yellow dust that is produced by a plant and that is carried to other plants of the same kind usually by wind or insects so that the plants can produce seeds

outbreak – n. a sudden start or increase of fighting or disease

species – n. group of animals or plants that are similar and can produce young animals or plants; a group of related animals or plants that is smaller than a genus

1 epidemic   

n.流行病；盛行；adj.流行性的，流传极广的

参考例句：

• That kind of epidemic disease has long been stamped out.那种传染病早已绝迹。
• The authorities tried to localise the epidemic.当局试图把流行病限制在局部范围。

2 syndrome   

n.综合病症；并存特性

参考例句：

• The Institute says that an unidentified virus is to blame for the syndrome. 该研究所表示,引起这种综合症的是一种尚未确认的病毒。
• Results indicated that 11 fetuses had Down syndrome. 结果表明有11个胎儿患有唐氏综合征。

3 rodents   

n.啮齿目动物( rodent的名词复数 )

参考例句：

• Rodents carry diseases and are generally regarded as pests. 啮齿目动物传播疾病，常被当作害虫对待。 来自《简明英汉词典》
• Some wild rodents in Africa also harbor the virus. 在非洲，有些野生啮齿动物也是储毒者。 来自辞典例句

4 beetles   

n.甲虫( beetle的名词复数 )

参考例句：

• Beetles bury pellets of dung and lay their eggs within them. 甲壳虫把粪粒埋起来，然后在里面产卵。 来自《简明英汉词典》
• This kind of beetles have hard shell. 这类甲虫有坚硬的外壳。 来自《现代汉英综合大词典》

5 moths   

n.蛾( moth的名词复数 )

参考例句：

• The moths have eaten holes in my wool coat. 蛀虫将我的羊毛衫蛀蚀了几个小洞。 来自《简明英汉词典》
• The moths tapped and blurred at the window screen. 飞蛾在窗帘上跳来跳去，弄上了许多污点。 来自《现代英汉综合大词典》

6 pollen   

n.[植]花粉

参考例句：

• Hummingbirds have discovered that nectar and pollen are very nutritious.蜂鸟发现花蜜和花粉是很有营养的。
• He developed an allergy to pollen.他对花粉过敏。

7 lizards   

n.蜥蜴( lizard的名词复数 )

参考例句：

• Nothing lives in Pompeii except crickets and beetles and lizards. 在庞培城里除了蟋蟀、甲壳虫和蜥蜴外，没有别的生物。 来自辞典例句
• Can lizards reproduce their tails? 蜥蜴的尾巴断了以后能再生吗？ 来自辞典例句

8 pollination   

n.授粉

参考例句：

• The flowers get pollination by insects.这些花通过昆虫授粉。
• Without sufficient pollination,the growth of the corn is stunted.没有得到充足的授粉，谷物的长势就会受阻。

9 parasite   

n.寄生虫；寄生菌；食客

参考例句：

• The lazy man was a parasite on his family.那懒汉是家里的寄生虫。
• I don't want to be a parasite.I must earn my own way in life.我不想做寄生虫，我要自己养活自己。