Study: Humans Give More Viruses to Animals Than They Give Us

Study: Humans Give More Viruses to Animals Than They Give Us

　　Some of the deadliest diseases to infect humans have come from pathogens that jumped from animals to people. The virus that causes AIDS, for example, came from chimpanzees. And many experts believe the virus that caused the COVID-19 pandemic came from bats.

　　But, as a new study shows, this disease exchange has not been just from animals to humans. In fact, research of all the publicly available viral genome sequences produced a surprising result: humans give about two times as many viruses to animals than they give to us.

　　The researchers looked at nearly 12 million virus genomes and found almost 3,000 times a virus jumped from one species to another. Of those, 79 percent involved a virus going from one animal species to another animal species. The remaining 21 percent involved humans. Of those, 64 percent were human-to-animal transmissions. Thirty-six percent were animal-to-human transmissions.

　　Scientists call the human-to animal transmission anthroponosis. Animal-to-human transmission is called zoonosis.

　　The animals affected¹ by anthroponosis included pets like cats and dogs; domesticated² animals like pigs, horses and cattle; birds such as chickens and ducks; primates³ such as chimpanzees, gorillas⁴ and howler monkeys; and other wild animals like raccoons and the African soft-furred mouse.

　　Wild animals were more likely to experience human-to-animal transmission than the other way around.

　　The study represents humans' large "impact on the environment and the animals around us," said Cedric Tan. He is a doctoral student in biology at the University College London Genetics Institute. He was a lead writer of the study, which appeared recently in the publication Nature Ecology & Evolution.

　　People and animals carry many microbes that can jump to another species through close contact. The study looked at viral transmissions involving all the vertebrate groups: mammals, birds, reptiles⁶, amphibians⁷ and fish.

　　Viruses go between species in the same ways viruses are transmitted between humans, Tan said. That includes "direct contact with infected fluids, or getting bitten by other species, amongst others."

　　But before the virus enters a different species, it must either have "the biological toolkit, or acquire host-specific adaptations, to enter the cells of the new host species and exploit their resources," Tan added.

　　Over thousands of years, pandemics that have killed millions of people have been caused by pathogens like viruses, bacteria and fungi⁸ that crossed over to people from animals.

　　Francois Balloux is director of the University College London Genetics Institute and one of the study's co-writers. He said a large majority of pathogens in humans came from animals at some point in time.

　　"The current biggest threat is probably bird flu H5N1, which is circulating in wild birds," he said. The main reason recent pathogen jumps can be so harmful is because the "population of host species has no pre-existing immunity⁹" to the new disease, he added.

　　In the 14th century, the bacterial¹⁰ disease bubonic plague killed millions of people in Europe, Asia, the Middle East and North Africa. It was caused by a bacteria normally found in wild rodents¹¹.

　　And present-day diseases like the Ebola virus similarly came from animals.

　　Most species-to-species transmissions are of little threat, Balloux added.

　　"In most cases, such infections lead nowhere, as the virus is poorly adapted and there is no onward¹² transmission in the new host," he said.

　　Words in This Story

　　pathogen — n. something such as a type of bacteria or a virus that causes disease

　　genome — n. the complete set of genes¹³ or genetic⁵ material present in a cell or organism.

　　domesticated — n. to breed or train to need and accept the care of human beings

　　impact — n. the act or force of one thing hitting another

　　microbe — n. an extremely small living thing that can only be seen with a microscope

　　vertebrate — n. an animal that has a backbone¹⁴

　　toolkit — n. a set of tools, especially one kept in a bag or box and used for a particular purpose.

　　adaptation — n. the process of changing to fit some purpose or situation

　　exploit — v. to get value or use from

　　host — n. an animal or plant in which another animal or plant lives and gets its food or protection

1 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

2 domesticated   

adj.喜欢家庭生活的；（指动物）被驯养了的v.驯化( domesticate的过去式和过去分词 )

参考例句：

• He is thoroughly domesticated and cooks a delicious chicken casserole. 他精于家务，烹制的砂锅炖小鸡非常可口。 来自《简明英汉词典》
• The donkey is a domesticated form of the African wild ass. 驴是非洲野驴的一种已驯化的品种。 来自《简明英汉词典》

3 primates   

primate的复数

参考例句：

• Primates are alert, inquisitive animals. 灵长目动物是机灵、好奇的动物。
• Consciousness or cerebration has been said to have emerged in the evolution of higher primates. 据说意识或思考在较高级灵长类的进化中已出现。

4 gorillas   

n.大猩猩( gorilla的名词复数 )；暴徒，打手

参考例句：

• the similitude between humans and gorillas 人类和大猩猩的相像
• Each family of gorillas is led by a great silverbacked patriarch. 每个大星星家族都由一个魁梧的、长着银色被毛的族长带领着。 来自《简明英汉词典》

5 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

6 reptiles   

n.爬行动物，爬虫( reptile的名词复数 )

参考例句：

• Snakes and crocodiles are both reptiles. 蛇和鳄鱼都是爬行动物。 来自《简明英汉词典》
• Birds, reptiles and insects come from eggs. 鸟类、爬虫及昆虫是卵生的。 来自《现代汉英综合大词典》

7 amphibians   

两栖动物( amphibian的名词复数 )； 水陆两用车； 水旱两生植物； 水陆两用飞行器

参考例句：

• The skin of amphibians is permeable to water. 两栖动物的皮肤是透水的。
• Two amphibians ferry them out over the sands. 两辆水陆两用车把他们渡过沙滩。

8 fungi   

n.真菌，霉菌

参考例句：

• Students practice to apply the study of genetics to multicellular plants and fungi.学生们练习把基因学应用到多细胞植物和真菌中。
• The lawn was covered with fungi.草地上到处都是蘑菇。

9 immunity   

n.优惠；免除；豁免，豁免权

参考例句：

• The law gives public schools immunity from taxation.法律免除公立学校的纳税义务。
• He claims diplomatic immunity to avoid being arrested.他要求外交豁免以便避免被捕。

10 bacterial   

a.细菌的

参考例句：

• Bacterial reproduction is accelerated in weightless space. 在失重的空间，细菌繁殖加快了。
• Brain lesions can be caused by bacterial infections. 大脑损伤可能由细菌感染引起。

11 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

12 onward   

adj.向前的，前进的；adv.向前，前进，在先

参考例句：

• The Yellow River surges onward like ten thousand horses galloping.黄河以万马奔腾之势滚滚向前。
• He followed in the steps of forerunners and marched onward.他跟随着先辈的足迹前进。

13 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

14 backbone   

n.脊骨，脊柱，骨干；刚毅，骨气

参考例句：

• The Chinese people have backbone.中国人民有骨气。
• The backbone is an articulate structure.脊椎骨是一种关节相连的结构。