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人类是否会将新冠病毒传染给动物?

人类是否会将新冠病毒传染给动物?

Carolyn Barbe 2020年09月11日
动物和人类在病毒传播方面有着漫长的共同的历史。

当今年年初中国武汉的一家活体农贸市场中发现了新型冠状病毒,人们就曾推断,病毒极有可能是从蝙蝠传播给人类。从那之后,我们关注的焦点一直是这种可怕疾病的全球人类感染者数量,这是可以理解的。目前全球新冠病毒感染人数已经超过2,800万人。

但新冠病毒除了在人类之间继续传播以外,有没有可能让动物界面临风险?这个问题的答案正在浮出水面,而且濒危物种和我们的家养宠物都会受到影响。

动物和人类在病毒传播方面有着漫长的共同的历史。去年,美国疾病预防与控制中心(Centers for Disease Control and Prevention)的公共卫生服务主任凯西•巴顿•贝拉维什在官网上发表的一份声明中称:“每年动物与人之间传播的疾病导致数以万计的美国人染病。”美国疾控中心表示,人类传染病约60%为人畜共患传染病,这意味着它们是由动物传播给人类(或者反之)。比如狂犬病、莱姆病、西尼罗河病毒和中东呼吸综合征等。

但新冠肺炎呢?答案很简单:新冠病毒从人向动物传播的病例虽然很少,但确实已经出现。根据人畜传播最终可能达到的规模,这种情况值得密切关注。

我们掌握的动物发病率数据少之又少。在武汉发布的一篇预印报告中,研究人员发现,他们检测了100多只家猫和流浪猫,其中约15%新冠肺炎呈阳性,但美国家养的猫、狗等物种感染新冠病毒的病例较为罕见。美国兽医协会(American Veterinary Medical Association)网站上表示,几乎没有证据证明家养动物容易感染新冠病毒,而且美国农业部(Agriculture Department)的数据库报告称,到目前为止,国家兽医服务实验室(National Veterinary Services Laboratories)确诊新冠肺炎呈阳性的动物不足40只。(巴顿•贝拉维什通过电子邮件告诉我说,被感染的动物“不一定出现症状……因此,我们无法确定美国有多少动物感染了新冠病毒。”)

中国香港的两只狗是已知最早感染新冠病毒的犬类。已知第一例人类到猫传播的病例在3月下旬发生于比利时。猫主人生病后,这只猫出现了腹泻、呕吐和呼吸困难等新冠肺炎的典型症状。它在9天后完全康复。事实上,巴顿•贝拉维什告诉我,确诊感染新冠病毒的多数动物仅出现了“较轻的症状,并且已经完全康复。”

除了初期的病例以外,家养猫犬新冠病毒检测呈阳性的病例极其罕见,而且这些病例似乎主要源于有症状或无症状的宠物主人将病毒传染给了他们亲爱的猫和狗狗。幸运的是,没有证据证明宠物会向人传播新冠病毒。巴顿•贝拉维什说,爱抚或者拥抱毛茸茸的爱宠将病毒从宠物传播给人的风险很低。

大型猫科动物也可能感染新冠病毒。纽约布朗克斯动物园(Bronx Zoo)发现,5只老虎和3只非洲狮出现了轻度呼吸道症状,经检测新冠病毒均呈阳性,但它们都已经完全康复。此事当时曾经被广泛报道。美国农业部称,这几只动物的传染源来自一名新冠病毒呈阳性但无症状的动物管理员,这位管理员是“一位活跃的病毒传播者”。巴顿•贝拉维什向我证实,除了南非有一只美洲狮被护理员感染以外,美国动物园内没有再出现更多感染病例。

西班牙、丹麦、荷兰和美国的貂养殖场内都爆发了新冠疫情,原因可能是养殖场内患病的工作人员。虽然目前动物向人传播病毒的情况并不明显,但荷兰的病例假设存在从貂向人类传播的可能。

当然,我们目前还处在摸索阶段。例如,《科学》杂志(Science)上发表的一篇研究报告发现,在实验室中,病毒不会在狗、猪、鸡、鸭等动物中复制或轻易传播。但猫比狗更容易在同类之间传播新冠病毒。有一份未公布的模拟研究显示,猿和非洲与亚洲的猴子可能“非常容易感染”新冠病毒。(需要特别注意的是,实验性和模拟性研究并不见得能体现自然环境下的病毒传播情况。动物在真实世界中可能不容易感染新冠病毒,这或许是相关数据增长缓慢的部分原因。)

但历史提醒我们要时刻保持警惕,因为之前病毒从人向其他物种传播,曾经对动物和鱼类造成了毁灭性的影响。有证据表明,在2002年至2003年的埃博拉疫情期间,有超过5,000只大猩猩死于这种病毒,尽管该证据曾经引发激烈争论。2015年,美国西海岸数千万海星患上了胃肠道消耗性疾病,许多海星死亡,罪魁祸首被认为是一场细小病毒疫情。新冠病毒是一种新型病毒,因此我们必须保证面临风险的野生动物和海洋生物不会因为我们没有为它们采取有效的保护措施而大规模死亡甚至灭绝。

目前,全球什么问题最值得担忧?可能是未经处理的人类排泄物。位于加拿大新斯科细亚省的戴尔豪斯大学(Dalhousie University)的科学家格雷厄姆•德莱尔和同事在一篇尚未发表的预印研究报告中预测,至少15种海洋哺乳动物容易感染新冠病毒,比如鲸、海豚、海豹、水獭和海狮等,有些甚至比人类还要脆弱。他们的研究基于对ACE2受体的分析。ACE2受体是病毒进入细胞的一种关键蛋白。(美国兽医协会指出,病毒复制和传播还需要其他过程,所以很难明确病毒传播的能力。)这些动物中包含一些濒危物种,它们被感染的途径可能是在动物园或水族馆里与人类直接接触,或者通过被人类污水中的新冠病毒污染的未经处理的废水。

意大利、澳大利亚和西班牙等国均在未经处理的废水中发现了新冠病毒,并且科学家证实,新冠病毒在被污染的水中几天甚至几周后依旧具有传染性。当然,问题是水中的病毒是否会导致海洋生物被感染。德莱尔告诉我,虽然目前还没有发现感染SARS-CoV-2的海洋哺乳动物,“……白鲸和海豚曾经被发现感染了相关的伽马冠状病毒。”例如,今年7月,圣迭戈海湾有4只海豚出现了胃肠道疾病的症状。

潜在的后果极其严重。一头白鲸曾经感染冠状病毒,出现了肺病和晚期肝衰竭,2000年有一只太平洋斑海豹在感染冠状病毒后死于肺炎。德莱尔说:“我们不知道新冠肺炎在这些哺乳动物当中会产生多么严重的后果。像人类感染新冠病毒一样,可能只出现了流鼻涕,也可能造成多器官损害。”如果动物感染这种病毒的数量极少,我们可能也无需担心。

为了帮助减少新冠病毒的影响和阻止病毒传播,德莱尔和同事们认为,重要的是妥善处理废水和未经处理的污水。他们甚至讨论了一种现在听起来有些不可思议的观点:针对濒危哺乳动物的疫苗项目,目标是实现群体免疫或者小群体免疫。事实上,用于避孕的疫苗早已成功应用于灰海豹,所以我们知道相关技术已经存在。

如果你感染了新冠肺炎,请记住你的宠物朋友可能会被感染,尽管到目前为止人向动物传播的病例很少。目前有许多研究正在进行当中,但美国疾控中心建议感染新冠病毒的宠物主人采取预防措施,保持卫生,避免与宠物直接接触。宠物主人在不具有传染性之前,尽可能让其他家庭成员照看宠物。在新冠肺炎疫情时代,与其他事情一样,想与爱宠拥抱需要等待一些时间。

我们还应该加入到拯救海洋生物的行动当中。海洋公园和水族馆可以限制游客接触面临风险的哺乳动物,从而减少病毒传播的风险。我们还能够与政策制定者、城市和卫生状况较差的欠发达国家合作,更好地监控水中的病毒,并妥善处理废水。德莱尔建议,至少应该对废水进行二级处理,最好进行紫外线或臭氧处理。他说这种处理方式可以消灭高达99%的病原体。

相关技术已经很成熟。例如,现有的无人机能够收集鲸分泌的粘液,从而有效监测新冠病毒等。我们不缺资源。我们需要进一步研究病毒在自然环境下的传播情况,加强监控和研究,并确定如何通过最有效的方式,阻止当前人类面临的这场疫情蔓延到动物王国。(财富中文网)

本文作者卡罗琳•巴伯担任急诊科医生已有25年。她是无家可归者工作项目“改变之轮”(Wheels of Change)的联合创始人,也是新书《暴走的药品:无知可能致命》(Runaway Medicine: What You Don't Know May Kill You)的作者。

译者:Biz

编译:陈怡轩、陈聪聪

当今年年初中国武汉的一家活体农贸市场中发现了新型冠状病毒,人们就曾推断,病毒极有可能是从蝙蝠传播给人类。从那之后,我们关注的焦点一直是这种可怕疾病的全球人类感染者数量,这是可以理解的。目前全球新冠病毒感染人数已经超过2,800万人。

但新冠病毒除了在人类之间继续传播以外,有没有可能让动物界面临风险?这个问题的答案正在浮出水面,而且濒危物种和我们的家养宠物都会受到影响。

动物和人类在病毒传播方面有着漫长的共同的历史。去年,美国疾病预防与控制中心(Centers for Disease Control and Prevention)的公共卫生服务主任凯西•巴顿•贝拉维什在官网上发表的一份声明中称:“每年动物与人之间传播的疾病导致数以万计的美国人染病。”美国疾控中心表示,人类传染病约60%为人畜共患传染病,这意味着它们是由动物传播给人类(或者反之)。比如狂犬病、莱姆病、西尼罗河病毒和中东呼吸综合征等。

但新冠肺炎呢?答案很简单:新冠病毒从人向动物传播的病例虽然很少,但确实已经出现。根据人畜传播最终可能达到的规模,这种情况值得密切关注。

我们掌握的动物发病率数据少之又少。在武汉发布的一篇预印报告中,研究人员发现,他们检测了100多只家猫和流浪猫,其中约15%新冠肺炎呈阳性,但美国家养的猫、狗等物种感染新冠病毒的病例较为罕见。美国兽医协会(American Veterinary Medical Association)网站上表示,几乎没有证据证明家养动物容易感染新冠病毒,而且美国农业部(Agriculture Department)的数据库报告称,到目前为止,国家兽医服务实验室(National Veterinary Services Laboratories)确诊新冠肺炎呈阳性的动物不足40只。(巴顿•贝拉维什通过电子邮件告诉我说,被感染的动物“不一定出现症状……因此,我们无法确定美国有多少动物感染了新冠病毒。”)

中国香港的两只狗是已知最早感染新冠病毒的犬类。已知第一例人类到猫传播的病例在3月下旬发生于比利时。猫主人生病后,这只猫出现了腹泻、呕吐和呼吸困难等新冠肺炎的典型症状。它在9天后完全康复。事实上,巴顿•贝拉维什告诉我,确诊感染新冠病毒的多数动物仅出现了“较轻的症状,并且已经完全康复。”

除了初期的病例以外,家养猫犬新冠病毒检测呈阳性的病例极其罕见,而且这些病例似乎主要源于有症状或无症状的宠物主人将病毒传染给了他们亲爱的猫和狗狗。幸运的是,没有证据证明宠物会向人传播新冠病毒。巴顿•贝拉维什说,爱抚或者拥抱毛茸茸的爱宠将病毒从宠物传播给人的风险很低。

大型猫科动物也可能感染新冠病毒。纽约布朗克斯动物园(Bronx Zoo)发现,5只老虎和3只非洲狮出现了轻度呼吸道症状,经检测新冠病毒均呈阳性,但它们都已经完全康复。此事当时曾经被广泛报道。美国农业部称,这几只动物的传染源来自一名新冠病毒呈阳性但无症状的动物管理员,这位管理员是“一位活跃的病毒传播者”。巴顿•贝拉维什向我证实,除了南非有一只美洲狮被护理员感染以外,美国动物园内没有再出现更多感染病例。

西班牙、丹麦、荷兰和美国的貂养殖场内都爆发了新冠疫情,原因可能是养殖场内患病的工作人员。虽然目前动物向人传播病毒的情况并不明显,但荷兰的病例假设存在从貂向人类传播的可能。

当然,我们目前还处在摸索阶段。例如,《科学》杂志(Science)上发表的一篇研究报告发现,在实验室中,病毒不会在狗、猪、鸡、鸭等动物中复制或轻易传播。但猫比狗更容易在同类之间传播新冠病毒。有一份未公布的模拟研究显示,猿和非洲与亚洲的猴子可能“非常容易感染”新冠病毒。(需要特别注意的是,实验性和模拟性研究并不见得能体现自然环境下的病毒传播情况。动物在真实世界中可能不容易感染新冠病毒,这或许是相关数据增长缓慢的部分原因。)

但历史提醒我们要时刻保持警惕,因为之前病毒从人向其他物种传播,曾经对动物和鱼类造成了毁灭性的影响。有证据表明,在2002年至2003年的埃博拉疫情期间,有超过5,000只大猩猩死于这种病毒,尽管该证据曾经引发激烈争论。2015年,美国西海岸数千万海星患上了胃肠道消耗性疾病,许多海星死亡,罪魁祸首被认为是一场细小病毒疫情。新冠病毒是一种新型病毒,因此我们必须保证面临风险的野生动物和海洋生物不会因为我们没有为它们采取有效的保护措施而大规模死亡甚至灭绝。

目前,全球什么问题最值得担忧?可能是未经处理的人类排泄物。位于加拿大新斯科细亚省的戴尔豪斯大学(Dalhousie University)的科学家格雷厄姆•德莱尔和同事在一篇尚未发表的预印研究报告中预测,至少15种海洋哺乳动物容易感染新冠病毒,比如鲸、海豚、海豹、水獭和海狮等,有些甚至比人类还要脆弱。他们的研究基于对ACE2受体的分析。ACE2受体是病毒进入细胞的一种关键蛋白。(美国兽医协会指出,病毒复制和传播还需要其他过程,所以很难明确病毒传播的能力。)这些动物中包含一些濒危物种,它们被感染的途径可能是在动物园或水族馆里与人类直接接触,或者通过被人类污水中的新冠病毒污染的未经处理的废水。

意大利、澳大利亚和西班牙等国均在未经处理的废水中发现了新冠病毒,并且科学家证实,新冠病毒在被污染的水中几天甚至几周后依旧具有传染性。当然,问题是水中的病毒是否会导致海洋生物被感染。德莱尔告诉我,虽然目前还没有发现感染SARS-CoV-2的海洋哺乳动物,“……白鲸和海豚曾经被发现感染了相关的伽马冠状病毒。”例如,今年7月,圣迭戈海湾有4只海豚出现了胃肠道疾病的症状。

潜在的后果极其严重。一头白鲸曾经感染冠状病毒,出现了肺病和晚期肝衰竭,2000年有一只太平洋斑海豹在感染冠状病毒后死于肺炎。德莱尔说:“我们不知道新冠肺炎在这些哺乳动物当中会产生多么严重的后果。像人类感染新冠病毒一样,可能只出现了流鼻涕,也可能造成多器官损害。”如果动物感染这种病毒的数量极少,我们可能也无需担心。

为了帮助减少新冠病毒的影响和阻止病毒传播,德莱尔和同事们认为,重要的是妥善处理废水和未经处理的污水。他们甚至讨论了一种现在听起来有些不可思议的观点:针对濒危哺乳动物的疫苗项目,目标是实现群体免疫或者小群体免疫。事实上,用于避孕的疫苗早已成功应用于灰海豹,所以我们知道相关技术已经存在。

如果你感染了新冠肺炎,请记住你的宠物朋友可能会被感染,尽管到目前为止人向动物传播的病例很少。目前有许多研究正在进行当中,但美国疾控中心建议感染新冠病毒的宠物主人采取预防措施,保持卫生,避免与宠物直接接触。宠物主人在不具有传染性之前,尽可能让其他家庭成员照看宠物。在新冠肺炎疫情时代,与其他事情一样,想与爱宠拥抱需要等待一些时间。

我们还应该加入到拯救海洋生物的行动当中。海洋公园和水族馆可以限制游客接触面临风险的哺乳动物,从而减少病毒传播的风险。我们还能够与政策制定者、城市和卫生状况较差的欠发达国家合作,更好地监控水中的病毒,并妥善处理废水。德莱尔建议,至少应该对废水进行二级处理,最好进行紫外线或臭氧处理。他说这种处理方式可以消灭高达99%的病原体。

相关技术已经很成熟。例如,现有的无人机能够收集鲸分泌的粘液,从而有效监测新冠病毒等。我们不缺资源。我们需要进一步研究病毒在自然环境下的传播情况,加强监控和研究,并确定如何通过最有效的方式,阻止当前人类面临的这场疫情蔓延到动物王国。(财富中文网)

本文作者卡罗琳•巴伯担任急诊科医生已有25年。她是无家可归者工作项目“改变之轮”(Wheels of Change)的联合创始人,也是新书《暴走的药品:无知可能致命》(Runaway Medicine: What You Don't Know May Kill You)的作者。

译者:Biz

编译:陈怡轩、陈聪聪

We think we know about the initial transmission of the coronavirus; it occurred at a live animal market in Wuhan, China, most likely from a bat to a person. In the time since, our attention has been understandably focused on the global human toll of this brutal disease, which already has reached a total of more than 28 million cases.

But how likely is it that, in addition to continually infecting each other, our human viral spread is also putting the animal world at risk? The answers to that question are emerging, and they carry implications both for endangered species and our own household pets.

Animals and humans have a long, common history when it comes to viruses. “Every year, tens of thousands of Americans get sick from diseases spread between animals and people,” said Casey Barton Behravesh, U.S. public health service director at the Centers for Disease Control and Prevention (CDC), in a statement posted to the organization’s website last year. The CDC says roughly 60% of human infectious diseases are zoonotic, meaning they’re transmitted by animals to people (or vice versa). Think of rabies, Lyme disease, West Nile virus, and MERS, among others.

But what about COVID-19? The short answer is that, although the numbers remain very low, human-to-animal transmission of the novel coronavirus has occurred. Depending upon what scale that ultimately achieves, it’s something worth watching closely.

We have very little prevalence data on animals. In a published preprint from Wuhan, researchers found that of more than 100 domestic and stray cats they tested, approximately 15% were positive for the coronavirus, but only rare cases of COVID-19 have been reported in domesticated cats, dogs, and other species in the U.S. The American Veterinary Medical Association website says that there’s little to no evidence that domestic animals are easily infected with the virus, and the Agriculture Department database reports that fewer than 40 animals so far have been confirmed COVID-positive by the National Veterinary Services Laboratories. (Barton Behravesh told me via email that infected animals “might or might not have any symptoms…and for this reason we don’t know for sure how many animals are infected in the U.S.”)

Two dogs in Hong Kong were among the first known cases to appear in canines. The first known human-to-cat transmission, meanwhile, occurred in Belgium in late March, where a sick owner’s cat developed typical coronavirus-like symptoms including diarrhea, vomiting, and breathing difficulties. The cat made a full recovery nine days later. In fact, Barton Behravesh told me, most of the animals diagnosed with COVID experienced only “mild illness and fully recovered.”

Since these initial cases, very rare reports of domesticated dogs and cats testing positive for coronavirus have appeared, and they appear to stem primarily from either symptomatic or asymptomatic pet owners transmitting the infection to their beloved felines and canines. Thankfully, there is little evidence of the reverse. The risk that petting or hugging your furry domestic companion might transmit the virus from the pet back to you, Barton Behravesh said, is considered low.

Big cats can get the coronavirus, too. As was widely publicized in April, New York’s Bronx Zoo found that five tigers and three African lions developed mild respiratory symptoms—and all tested positive for the virus, though each recovered without incident. Transmission was felt to have occurred from an asymptomatic but positive zookeeper “who was actively shedding virus,” according to the Agriculture Department. Barton Behravesh confirmed to me that no further outbreaks of the coronavirus at zoos in the U.S have been reported, though a single puma in South Africa was infected by its caretaker.

We’ve seen COVID-19 outbreaks in other animals, including on mink farms in Spain, Denmark, the Netherlands, and the U.S., where it’s believed that ill farm workers were responsible for the outbreaks. And while animal-to-human transmission is felt to be insignificant at this time, cases in the Netherlands hypothesize possible spread from minks to humans.

Certainly, we’re learning as we go. For example, research reported in Science magazine found that in the laboratory, the virus either did not replicate or did not spread easily in dogs, pigs, chickens, or ducks. Cats, meanwhile, appeared able to pass along the coronavirus much easier to one another than were dogs. And there’s an unpublished modeling study that shows apes and African and Asian monkeys are likely to be “highly susceptible” to COVID-19. (It is important to remember that experimental and modeling studies do not necessarily reflect how infection will occur under natural conditions. Animals may not be as easily infected in the real world—perhaps that’s part of the reason the numbers are so low.)

Still, history suggests we need to have our guard up, as the spread of viruses to other species previously has had devastating effects on animal and fish populations. Though once hotly debated, the evidence shows that during the Ebola outbreak of 2002–03, more than 5,000 gorillas died of the virus. In 2015, an outbreak of parvovirus was thought to be responsible for a gastrointestinal wasting illness that affected hundreds of millions of starfish off America’s West Coast, many of which succumbed. Given that the coronavirus is a novel virus, we need to ensure that our at-risk wild animal and sea life populations do not experience massive die-offs or suffer extinctions because we failed to act to protect them.

What’s our concern globally right now? Above all else, it may well be untreated human waste. At Dalhousie University in Nova Scotia, scientist Graham Dellaire and his cohorts predicted in an unpublished preprint study that at least 15 species of marine mammals, including whales, dolphins, seals, otters, and sea lions, are susceptible—or potentially more susceptible than humans—to coronavirus infection. This is based on their analysis of ACE2 receptors, the key protein for virus entry. (The American Veterinary Medical Association notes that other processes are necessary for a virus to replicate and spread, so it is difficult to make definitive statements regarding the ability of the virus to transmit.) Some of these species are endangered, and their infection would likely occur either through direct contact with humans at zoos or aquariums or via untreated wastewater that is contaminated with the coronavirus from human sewage.

Several countries, including Italy, Australia and Spain, have detected the coronavirus in untreated wastewater, and scientists have shown that previous coronaviruses remained infectious in the contaminated water for days to weeks. The question, of course, is whether virus present in the water will lead to actual infections in sea life. Dellaire told me that while no marine mammals have been found yet infected with SARS-CoV-2, “…beluga whales and dolphins have been found to be infected by related gammacoronaviruses.” That includes four dolphins in San Diego Bay who were symptomatic with a gastrointestinal illness this past July.

The potential consequences are grave. Coronavirus infections were linked to a beluga whale that experienced lung disease and terminal liver failure, and Pacific harbor seals that died from pneumonia in 2000. Said Dellaire, “We do not know how bad the disease could be in these mammals. It could be a sniffle or multi-organ damage, just like COVID-19 in humans.” It also could be nothing, if transmission is negligible.

To help mitigate the impact and prevent coronavirus transmission, Dellaire and his colleagues believe proper treatment of wastewater and raw sewage is essential. They even discuss what right now may sound inconceivable: a potential vaccination program for endangered mammal populations in which the goal is to achieve herd immunity, or perhaps pod immunity. In fact, vaccines have already been used successfully in gray seals for contraceptive purposes, so we know the technology is there.

If you get COVID, know that your furry friends and oceangoing pals may be susceptible, though we have seen only rare spread so far. While many studies are underway, the CDC recommends that pet owners infected with the coronavirus maintain hygiene precautions and restrain from having direct contact with their animals. If possible, another member of the family should care for the pets until the individual is no longer infectious. Like so much else in the age of COVID, snuggle time will have to wait.

But let’s help save the Shamus of the world, too. Let’s limit visitor contact with at-risk mammals at marine parks and aquariums to reduce viral exposure. Let’s work also with policymakers, cities, and underdeveloped countries with poor sanitation to better monitor live virus in our waters and treat wastewater appropriately. Dellaire recommends at least secondary treatment of wastewater or—even better—UV or ozone treatment, which he says destroys up to 99% of pathogens.

The technology is ready. A drone already exists, for example, that can collect mucus from a whale and feasibly detect viruses like the coronavirus. We have the resources. We need to investigate further how much transmission is occurring under natural conditions, conduct more surveillance and studies, and then determine how we might best prevent our now-human pandemic from becoming a problem for the animal kingdom as well.

Carolyn Barber has been an emergency department physician for 25 years. She is cofounder of the homeless work program Wheels of Change and author of a new book, Runaway Medicine: What You Don’t Know May Kill You.

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