中国最大的水貂养殖场(全球最大水貂皮产国丹麦为何要扑杀国内水貂)

当地时间11月4日，世界上最大的水貂皮生产国丹麦表示将扑杀该国所有水貂，数量高达1500万到1700万只。丹麦水貂养殖者协会主席称，政府的决定对该行业和丹麦来说都是一场灾难。

目前，丹麦已确认有214例确证感染新冠病毒的病例与水貂有关，关系到5个水貂农场。

丹麦总理梅特·弗雷德里克森4日指出，新冠病毒在水貂群体中发生了变异，而这种变异的病毒已经传染给了人类。

6日，世卫组织表示，有迹象显示，丹麦水貂携带的新冠病毒出现的一些变异，可能会产生影响，但还需要进一步研究。

Denmark has discovered a new, mutated strain of the coronavirus stemming from mink farms in the northern part of the country, which authorities say could evade future COVID-19 vaccines.

To prevent human contagion, the government ordered the culling of the entire mink population of 17 million in Denmark, one of the world's biggest mink pelt producers.

我们目前对这种变异病毒了解多少呢？

Here's what's known about the Danish strain:

What are the mink strains and why do they matter?

丹麦血清研究所（SSI）的一份报告指出，目前在丹麦发现了5种不同的貂类变异新冠肺炎病毒，即Cluster 1— Cluster 5。初步研究表明，与非突变型病毒相比， Cluster 5对抗体敏感性降低。

Denmark has identified five variants of the virus stemming from minks, but only one – known as Cluster 5 – showed "reduced sensitivity" towards antibodies, according to Denmark's State Serum Institute (SSI), which deals with infectious diseases.

State epidemiologist Kare Molbak said cluster 5 was not more dangerous than other strains or more infectious.

Clusters 2, 3 and 4 are still being studied for reduced sensitivity, which has already been ruled out in the cluster 1 variant.

How far has the mutated virus spread?

在丹麦，从6月初到10月中旬，在5102个样本中，有214例检测到来自貂类变异新冠肺炎病毒。8月和9月在5个水貂养殖场和12个样本中发现了Cluster 5病毒。但此后，就没有新病例上报了。

在丹麦北部发现的毒株中，Cluster 5病毒约占5%，但这种病毒并没有出现在丹麦以外的地方，目前还不清楚它为什么会在丹麦出现。

Cluster 5 has been found on five mink farms in Northern Denmark and 12 cases were registered in humans in the same Danish region in August and September, but none has been registered since then, according to SSI.

"We can simply hope that it no longer exists to the same extent," Molbak told a news conference on Thursday, adding that nothing could be said with certainty.

Cluster 5 makes up around 5 percent of the strains found in Northern Denmark, but it has not appeared outside the country and it was not immediately clear why it emerged in Denmark.

What's the implication for future vaccines?

在世界卫生组织6日举行新闻发布会上，世卫组织首席研究员苏米亚·斯瓦米纳坦表示，目前说这种变异病毒将影响即将到来的新冠肺炎疫苗还为时过早。

但是SSI的实验室研究表明，这种新菌株的刺突糖蛋白发生了突变，这可能会给目前的新冠疫苗研发带来问题——目前大多数疫苗都专注于抑制刺突糖蛋白。

It's too early to say what, if any, impact the cluster 5 mutation could have on the efficacy of potential vaccines, Soumya Swaminathan, the World Health Organization's chief scientist, said on Friday.

But SSI's initial laboratory studies show the new strain had mutations on its so-called spike protein, which invades and infects healthy cells.

This could pose a problem to future vaccines that are currently in development as most of them focus on disabling the spike protein.

Data have been shared with international counterparts, including the WHO and the European Centre for Disease Prevention and Control (ECDC), and the genome sequences of the mutated virus strains have been logged in the Global Initiative on Sharing All Influenza Data (GISAID).

SSI said it would continue to share its findings.

Why is the virus spreading among minks?

世卫组织卫生紧急项目负责人迈克尔·瑞安表示，令人担心的是，水貂这样的哺乳动物是很适合新冠病毒的动物宿主。目前，新冠病毒已在丹麦、荷兰、西班牙和美国等地的水貂养殖场爆发。

而水貂的养殖环境十分拥挤，使病毒的传播变得非常容易。

Minks appear to be susceptible to the new virus and "good reservoirs" for the virus, the WHO said on Thursday. Outbreaks have occurred on mink farms in Denmark, the Netherlands, Spain and the United States.

As minks are kept in cages in close proximity to each other, the virus can spread easily.

Why humans?

哥本哈根大学的病毒学家艾伦·兰德鲁普·汤姆森表示，貂和人类呼吸道细胞表面的血管紧张素转化酶具有相似的生物学特性，这使貂更容易感染适应人类的病毒。

迈克尔·瑞安也坦言道，这种病毒总是有可能再次出现在人类身上。

Minks and humans have a similar biological trait regarding a so-called ACE2-enzyme expressed by cells of the respiratory tract, which makes it easier for minks to be infected with a virus that has adapted to humans, Allan Randrup Thomsen, a virologist at Copenhagen University, told Reuters.

Mike Ryan, the WHO's top emergencies expert, said "there's always the potential that this can come back to humans."

"That is a concern because mammal species like mink are very good hosts and the virus can evolve within those species especially if they are in large numbers packed closely together," he said.

Are other livestock at risk?

瑞安表示，其他农场动物，如猪和家禽，感染这种新冠病毒的风险要低得多，因为农场有“非常严格”的生物安全措施，以防止病毒跨越物种屏障。

The risk is much lower in other farm animals, such as pigs and poultry, because farms have "very strict" biosecurity in place to prevent viruses jumping the species barrier, the WHO's Ryan said on Friday.

Tests have failed to infect swine, while cattle had been infected to only "a very small degree," according to the Danish Veterinary and Food Administration.

It said a sample taken from a gull's foot tested positive for the novel coronavirus, but there was no evidence it had infected birds.

Is the mutation a worry?

病毒的突变时刻都在发生。病毒通过适应新环境而生存，但其实冠状病毒的大多数突变都是无害的。

Mutations in viruses happen all the time. Viruses survive by adapting to new environments and most mutations of the coronavirus are harmless.

Two factors are involved in the mutation, Molbak said. First, the virus has to adapt to its new host. Second, when a virus enters a new population, a lot of antibodies are created in the population, which is commonly known as herd immunity.

The virus responds by creating so-called antibody escape mutants, which try and avoid the antibodies in the community.

What are other countries and the WHO doing?

世卫组织欧洲地区官员凯瑟琳·斯莫尔伍德表示，病毒随着时间发生基因改变“完全正常……我们十分谨慎地追踪这些变化”，目前各国政府和卫生机构无需改变防疫措施。

The WHO said it is looking at biosecurity around mink farms in countries across the world to prevent further "spillover events."

Discovery of the mutation should not alter what governments and authorities around the world do to control the pandemic, it said on Thursday.

Britain said on Friday it would require all travelers arriving from the Nordic country to self-isolate on arrival as a result of the outbreak, but it did not consider them to be a risk to the country.