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The writer is a science commentator
作者是一位科学评论家
In 2022, Bass Rock, a volcanic outcrop off the Scottish coast that houses the world’s largest colony of northern gannets, became a graveyard. Thousands of gannets were wiped out by a bird flu now thought to have killed millions of wild birds worldwide and devastated poultry flocks.
2022年，位于苏格兰海岸外的火山岩石巴斯岩(Bass Rock)，世界上最大的北方鲣鸟群落的家园，变成了一片鸟类墓地。一种鸟类流感导致数以千计的鲣鸟死亡，据现在的认知，这种流感已经在全球范围内导致数百万只野生鸟类死亡，并对家禽群体造成了毁灭性的打击。
Highly pathogenic avian influenza, or HPAI, became a zombie scourge that, unlike seasonal predecessors, never really disappeared. The virus that causes it, H5N1, has since jumped into species including mink, sea lions, dolphins, porpoises, otters and cats — and now cattle.
高致病性禽流感(HPAI)已成为一种僵尸灾害，与其季节性的前身不同，它从未真正消失过。引起它的病毒H5N1已经感染了包括水貂、海狮、海豚、鼠海豚、水獭和猫在内的物种，现在又传播到了牛。
As of Monday, nine US states had reported outbreaks in dairy cattle. One dairy worker in Texas has also tested positive. Viral fragments have been found in the country’s milk supply. Now, a US genomic analysis suggests a variant known as 2.3.4.4b has been spreading silently in cattle for months, perhaps since December.
截至周一，美国已有九个州报告了奶牛疫情。得克萨斯的一名奶制品工人也检测出阳性。在该国的牛奶供应中已发现病毒片段。现在，美国的一项基因组分析表明，一种名为2.3.4.4b的变异病毒可能自去年12月以来在牛群中悄然传播。
The virus does not usually pass from human to human but its undetected march into new mammalian hosts is not to be taken lightly, given that every infection offers the chance to mutate. The US Centers for Disease Control and Prevention says the risk to public health is low but it is preparing for the possibility that the flu becomes more transmissible between people. Now is not a time for paranoia but there is a case for extreme vigilance.
这种病毒通常不会在人与人之间传播，但它在未被发现的情况下进入新的哺乳动物宿主，这一点不容小觑，因为每一次感染都有机会发生变异。美国疾病控制与预防中心(Centers for Disease Control and Prevention)表示，对公众健康的风险很低，但它正在为流感在人与人之间传播的可能性做准备。现在不是疑神疑鬼的时候，但有理由保持高度警惕。
Exactly how bird flu made the leap into cattle is unclear. Birds shed the virus orally, nasally and through their urine and faeces; cows could have ingested contaminated feed or water. Scientists believe the virus then spread between cows through mechanical methods, such as shared milking machines, rather than through the air. According to the UK government, this strain is not circulating in Europe.
禽流感如何感染牛群尚不明确。鸟类通过口腔、鼻腔以及尿液和粪便排出病毒；牛可能通过摄入受污染的饲料或水源而感染。科学家认为，病毒在牛之间的传播更多的是通过机械方式，如共用的挤奶机，而非空气传播。根据英国政府的报告，这种病毒在欧洲并未流行。
The World Health Organization has expressed “great concern” and advised caution. Paul Digard, an influenza virologist at the Roslin Institute, Edinburgh University, told me this week that the threat level had risen: “Firstly, cow infections with avian flu on this scale is something new; what else has the virus ‘learnt’ to do with this latest round of genetic changes? Secondly, infecting dairy cows offers more opportunities to infect humans.”
世界卫生组织(World Health Organization)对此表示“极度关注”，并建议采取谨慎行动。爱丁堡大学(Edinburgh University)罗斯林研究所(Roslin Institute)的流感病毒学家保罗•迪加德(Paul Digard)本周告诉我，威胁级别已经提升：“首先，这种规模的牛感染禽流感是新的现象；在这最新一轮的基因变化中，病毒还学到了什么新的能力？其次，感染奶牛为感染人类提供了更多的可能性。”
The US Food and Drug Administration advises against consuming raw (unpasteurised) milk products, to guard against pathogens such as salmonella and E-coli; H5N1 is now also on the list. The odds of becoming infected by drinking pasteurised milk is deemed very low, given that testing so far shows no live infectious virus in the samples.
美国食品和药物管理局建议不要食用未经巴氏杀菌的生乳制品，以防沙门氏菌和大肠杆菌等病原体的感染；H5N1现在也被列入了这个名单。由于迄今为止的检测显示样本中没有活的传染性病毒，因此饮用巴氏杀菌牛奶被感染的几率被认为非常低。
However, the presence of virus fragments in pasteurised milk points to the possibility of asymptomatic infected cows, meaning the virus could be spreading under the radar. The US Department of Agriculture, which has banned infected cattle from crossing state borders, has been urged to scale up testing.
然而，巴氏消毒牛奶中病毒片段的存在，暗示了可能存在无症状感染的奶牛，这意味着病毒可能在我们的监测范围之外悄然传播。美国农业部已禁止感染的牛只跨州运输，并被敦促加大检测力度。
The infected dairy worker had conjunctivitis rather than respiratory symptoms; avian flu viruses struggle to latch on effectively to receptors in the human upper respiratory tract. But if the virus can get in, perhaps through high doses, it can be lethal: since 1997, H5N1 has killed about half of the roughly 900 people infected with it.
受感染的奶制品工人出现的是结膜炎而非呼吸道症状；禽流感病毒很难有效地附着在人类上呼吸道的受体上。但是，如果病毒能够侵入，可能是通过高剂量，它就可能致命：自1997年以来，H5N1已经导致大约900名感染者中的一半死亡。
One concern is “reassortment”: when two flu viruses circulating in the same infected animal swap genetic material. “H5N1 in pigs would be a very large, exceedingly red flag”, Digard warns, “given the frequency with which humans and pigs have exchanged [flu] viruses over the last 100 years.” The respiratory tracts of pigs show similarities to ours, meaning that a swine-adapted flu virus might not require many changes to threaten us.
一个令人担忧的现象是“重组”：当两种流感病毒在同一感染动物体内交换遗传物质时。迪加德警告说，“H5N1在猪中将是一个非常大的、极其危险的警告信号，考虑到过去100年人类和猪之间频繁交换流感病毒的情况。”猪的呼吸道与我们的相似，这意味着一种适应猪的流感病毒可能不需要太多改变就能对我们构成威胁。
The world is reasonably adept at dealing with seasonal flu, with global surveillance and an infrastructure for producing seasonal flu vaccines matched to circulating strains. There are also antivirals. But pandemic flu, especially caused by an animal virus to which humans have zero immunity, is a different prospect.
全球在应对季节性流感方面已经相当熟练，拥有全球监测和生产与流行病毒株相匹配的季节性流感疫苗的基础设施，还有抗病毒药物。然而，大流行性流感，特别是由人类对其没有免疫力的动物病毒引起的，这是一个完全不同的挑战。
There are existing, pre-authorised pandemic preparedness vaccines that can be adapted in a hurry, including ones from GSK and AstraZeneca targeting H5N1. Once the exact pandemic strain is identified, it can be included for production and further approval.
现有的、已获授权的大流行病防备疫苗，包括葛兰素史克(GSK)和阿斯利康公司针对H5N1的疫苗，都可以在短时间内进行调整。一旦确定了确切的大流行毒株，就可以将其纳入生产范围并进一步审批。
Interestingly, the CDC has now shared the candidate vaccine virus 2.3.4.4b with manufacturers. How quickly things can move from here is another question — one that deserves an answer sooner rather than later.
有趣的是，美国疾病控制中心(CDC)现已与制造商共享了候选疫苗病毒2.3.4.4b。接下来事情能以多快的速度发展是另一个问题——这是一个我们应该尽早找到答案的问题。