It seems to be caused by co-infection with two different viruses
這似乎是因兩種不同病毒共同感染所引起。
Jul 27th 2022
In april mysterious cases of hepatitis, an inflammation of the liver, began appearing in children around the world. They were not caused by the hepatitis viruses that typically cause the illness.
一種肝臟發炎的神秘肝炎病例，在4月開始出現於世界各地的兒童身上。它們不是由，通常導致此種疾病的肝炎病毒所引起。
The World Health Organisation has reported more than 1,000 probable cases in 35 countries. Some children have required liver transplants and at least 22 have died. Researchers have been scrambling to find the cause.
世界衛生組織已經報告，在35個國家中，有1千多起可能的病例。有些兒童已經需要肝臟移植，至少22人已經死亡。
Two studies posted this week on medRxiv, a preprint server, propose an answer—co-infection with two common and usually innocuous viruses, probably helped by certain gene variations in the children who fell ill. sars-cov-2 was ruled out as a culprit.
本週在預印本伺服器《medRxiv》(是醫學、臨床及相關之健康科學領域開放獲取的預印本資料庫，由冷泉港實驗室、BMJ出版集團和耶魯大學聯合建立)上發布的兩項研究，提出了一個答案。同時感染兩種常見且通常無害的病毒，這可能得益於患病兒童的某些基因變異。第二型嚴重急性呼吸系統徵候群-冠狀病毒(SARS-CoV-2：Severe Acute Respiratory Syndrome Coronavirus-2)被排除為一種罪魁禍首。
One of the infections seems to be from human adenovirus, a common bug in children that causes stomach upsets but does not make them very ill. A cluster of the strange hepatitis cases appeared shortly after a spike in adenovirus infections, though it was unclear what role the virus might be playing, because it is often present in healthy children too.
其中一種感染似乎來自人類腺病毒，這是一種於兒童中，引起胃部不適，但不會使他們病得很重的常見病原體。在腺病毒感染高峰後不久，出現了一串奇怪的肝炎病例。不過，該種病毒可能扮演什麼角色不詳。因為，它也經常存在於健康兒童中。
In the latest research, led by teams at the University of Glasgow and University College London, researchers investigated the blood and livers of 26 children with the strange hepatitis and compared the results with those from more than 100 children of the same age, including healthy children, children with adenovirus but normal liver function, and children with hepatitis for which the cause was known.
在由英國蘇格蘭格拉斯哥大學及倫敦大學學院等團隊領導的最新研究中，研究人員們調查研究了26名，罹患此種奇怪肝炎兒童的血液及肝臟，並將結果與那些來自100多名同齡兒童的結果進行比較。這些兒童包括健康的兒童、具有腺病毒但肝功能正常的兒童及罹患原因不明之肝炎的兒童。
Collectively, the two studies found that 25 out of the 26 children with the mysterious hepatitis were also infected with adeno-associated virus 2 (aav2). This virus (pictured left) was rarely found in the children without that form of hepatitis and, when present in them, it was in much lower quantities.
這兩項研究共同發現，這26名罹患此種神秘肝炎的兒童中，有25人也感染了腺相關病毒2 (aav2)。這種病毒很少在沒有這種肝炎形式的兒童身上被發現，且當在他們身上出現時，其數量少很多。
aav2 is a parvovirus that cannot replicate on its own but needs assistance from a “helper” virus such as an adenovirus or a herpesvirus. It is not known for causing illness but it is very contagious. Most children are exposed to it at a young age and it lays dormant in the cells, including those of the liver, until infection with a helper virus triggers its replication.
aav2是一種無法自行複製，而需要來自諸如腺病毒或皰疹病毒等“輔助”病毒之協助的微型濾過性病毒。它不以引起疾病而聞名，不過具有很強的傳染性。大多數兒童在小時候就接觸到，之後它在細胞中處於休眠狀態，包括肝臟細胞，直到感染輔助病毒才觸發其複製。
The results from the two studies suggest that coinfection by aav2 and adenovirus—or sometimes possibly a herpesvirus called hhv6, which was found in a few children—is the cause of the mysterious hepatitis illness.
來自這兩項研究的結果暗示，aav2及腺病毒(或有時可能是在少數兒童身上所發現，被稱為hhv6的皰疹病毒)的共同感染，是此種神秘肝炎疾病的原因。
Given how much aav2 and adenovirus circulate, lots of children probably get co-infected. Why, then, do only a small number of them develop the strange hepatitis? The researchers in Glasgow looked for an answer in the children’s genes.
鑒於aav2及腺病毒的傳播量，很多兒童可能會同時感染。那麼，為何只有少數兒童罹患此種奇怪肝炎？格拉斯哥大學的研究人員們，在兒童的基因中尋找答案。
In eight of the nine children with the strange hepatitis they found variations in the Human Leukocyte Antigen gene that were not commonly found in the 58 comparison children. The prevalence of these specific variations is highest in northern Europe—the region where most of the strange hepatitis cases have been reported.
在9名罹患此種奇怪肝炎的8名兒童中，他們在人類白細胞抗原基因中，發現若干變異。在58名對照的兒童中，此些變異並不普遍被發現。這些特定變異的盛行率在北歐最高。這是大多數此種奇怪肝炎病例，已經被報告的地區。
It is unclear how aav2 is causing the illness. The researchers did not find viral particles in the samples taken when the children were ill, but detected large amounts of RNA traces of aav2—which suggest that copious replication had happened in the past.
aav2如何導致這種疾病，目前不詳。此些研究人員在孩子生病時，採集的樣本中，沒有發現病毒粒子。不過，檢測到大量aav2的RNA蹤跡。這暗示，過去曾發生過大量複製。
This means that an indirect viral mechanism may be responsible, such as an immune reaction to aav2 that leads, in rare cases, to acute liver inflammation.
這意味著，一種間接的病毒機制或是原因。諸如在極少數情況下，導致急性肝臟炎症之對aav2的一種免疫反應。
Such cases of unexplained hepatitis are not new. But lowered immunity to viruses among children as a result of less mixing during the covid-19 pandemic led to many such cases at the same time. The world is acutely aware that exposure to novel viruses can cause pandemics, but a lack of exposure to bugs can cause problems too.
這種原因不明的肝炎病例並不新鮮。不過，由於在2019冠狀病毒症(COVID-19：Coronavirus Disease-19)大流行期間較少交往，於兒童之間對諸多病毒降低的免疫力，在此同時導致了許多此類病例。世界敏銳地意識到，曝露於新病毒會引發流行病。不過，缺乏曝露於病原菌也會導致問題的意識。
網址：https://www.economist.com/science-and-technology/2022/07/27/the-cause-of-a-new-type-of-hepatitis-in-children-is-found?utm_content=article-link-9&etear=nl_today_9&utm_campaign=a.the-economist-today&utm_medium=email.internal-newsletter.np&utm_source=salesforce-marketing-cloud&utm_term=8/1/2022&utm_id=1274127
翻譯：許東榮
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