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The writer is a science commentator
作者是一位科學評論家
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，位於蘇格蘭海岸外的火山岩石巴斯巖(Bass Rock)，世界上最大的北方鰹鳥羣落的家園，變成了一片鳥類墓地。一種鳥類流感導致數以千計的鰹鳥死亡，據現在的認知，這種流感已經在全球範圍內導致數百萬只野生鳥類死亡，並對家禽羣體造成了毀滅性的打擊。
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)已成爲一種殭屍災害，與其季節性的前身不同，它從未真正消失過。引起它的病毒H5N1已經感染了包括水貂、海獅、海豚、鼠海豚、水獺和貓在內的物種，現在又傳播到了牛。
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.
截至週一，美國已有九個州報告了奶牛疫情。德克薩斯的一名奶製品工人也檢測出陽性。在該國的牛奶供應中已發現病毒片段。現在，美國的一項基因組分析表明，一種名爲2.3.4.4b的變異病毒可能自去年12月以來在牛羣中悄然傳播。
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.
這種病毒通常不會在人與人之間傳播，但它在未被發現的情況下進入新的哺乳動物宿主，這一點不容小覷，因爲每一次感染都有機會發生變異。美國疾病控制與預防中心(Centers for Disease Control and Prevention)表示，對公衆健康的風險很低，但它正在爲流感在人與人之間傳播的可能性做準備。現在不是疑神疑鬼的時候，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.
禽流感如何感染牛羣尚不明確。鳥類透過口腔、鼻腔以及尿液和糞便排出病毒；牛可能透過攝入受汙染的飼料或水源而感染。科學家認爲，病毒在牛之間的傳播更多的是透過機械方式，如共用的擠奶機，而非空氣傳播。根據英國政府的報告，這種病毒在歐洲並未流行。
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.”
世界衛生組織(World Health Organization)對此表示「極度關注」，並建議採取謹慎行動。愛丁堡大學(Edinburgh University)羅斯林研究所(Roslin Institute)的流感病毒學家保羅•迪加德(Paul Digard)本週告訴我，威脅級別已經提升：「首先，這種規模的牛感染禽流感是新的現象；在這最新一輪的基因變化中，病毒還學到了什麼新的能力？其次，感染奶牛爲感染人類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.
美國食品和藥物管理局建議不要食用未經巴氏殺菌的生乳製品，以防沙門氏菌和大腸桿菌等病原體的感染；H5N1現在也被列入了這個名單。由於迄今爲止的檢測顯示樣本中沒有活的傳染性病毒，因此飲用巴氏殺菌牛奶被感染的幾率被認爲非常低。
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，暗示了可能存在無症狀感染的奶牛，這意味著病毒可能在我們的監測範圍之外悄然傳播。美國農業部已禁止感染的牛隻跨州運輸，並被敦促加大檢測力度。
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.
受感染的奶製品工人出現的是結膜炎而非呼吸道症狀；禽流感病毒很難有效地附著在人類上呼吸道的受體上。但是，如果病毒能夠侵入，可能是透過高劑量，它就可能致命：自1997年以來，H5N1已經導致大約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.
一個令人擔憂的現象是「重組」：當兩種流感病毒在同一感染動物體內交換遺傳物質時。迪加德警告說，「H5N1在豬中將是一個非常大的、極其危險的警告信號，考慮到過去100年人類和豬之間頻繁交換流感病毒的情況。」豬的呼吸道與我們的相似，這意味著一種適應豬的流感病毒可能不需要太多改變就能對我們構成威脅。
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.
全球在應對季節性流感方面已經相當熟練，擁有全球監測和生產與流行病毒株相匹配的季節性流感疫苗的基礎設施，還有抗病毒藥物。然而，大流行性流感，特別是由人類對其沒有免疫力的動物病毒引起的，這是一個完全不同的挑戰。
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.
現有的、已獲授權的大流行病防備疫苗，包括葛蘭素史克(GSK)和阿斯特捷利康公司針對H5N1的疫苗，都可以在短時間內進行調整。一旦確定了確切的大流行毒株，就可以將其納入生產範圍並進一步審批。
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，美國疾病控制中心(CDC)現已與製造商共享了候選疫苗病毒2.3.4.4b。接下來事情能以多快的速度發展是另一個問題——這是一個我們應該儘早找到答案的問題。