When flu strikes, why are some family members reduced to shivering wrecks under their duvets, while others get off with little more than a snuffle?
當(dāng)流感來襲時(shí)，為什么有些人蜷縮在羽絨被下瑟瑟發(fā)抖，而有的人最多就是有點(diǎn)鼻塞呢？
Scientists now have an answer, showing that the generation you belong to - and even the year of your birth - predicts how vulnerable you will be to a given strain of seasonal virus.
科學(xué)家們近日給出的答案顯示，人們出生的年代甚至是年份預(yù)示著其抵御特定種類季節(jié)性流感的能力。
The flu virus a person first encounters as a child, they found, leaves a permanent "imprint" on the immune system, giving them robust protection against similar strains and much weaker protection against less closely related varieties of the illness.
他們發(fā)現(xiàn)，兒時(shí)感染的流感病毒會在一個人的免疫系統(tǒng)上留下永久“印記”，人們由此獲得對類似疾病的強(qiáng)大免疫力，而對不太相似的疾病的抵抗力就弱得多。
Michael Worobey, head Ecology and Evolutionary Biology at the University of Arizona and a senior author of the study, said: "It's not the age, it's the birth year that matters."
美國亞利桑那大學(xué)生態(tài)與進(jìn)化生物學(xué)專家、該研究報(bào)告的資深作者邁克爾 伍羅貝稱，“這不是年齡的問題，而是和出生年份有關(guān)�！�
In future, seasonal vaccines could be targeted at people of particular ages who are most likely to benefit, and in pandemics when medications are scarce, vulnerable age ranges could be prioritised for protective measures.
未來，可以根據(jù)特定年齡區(qū)分季節(jié)性流感疫苗最能受益的人群。當(dāng)流感大爆發(fā)、藥物稀缺時(shí)，可以對抵抗力低的年齡群體采取優(yōu)先保護(hù)措施。
"It's breaking new ground for flu, where predictions are really hard," said Worobey. "For any given potential pandemic virus, we can actually now say ... this is the age group that you can expect is going to end up in hospital dying and this is the age group who will be protected."
伍羅貝說，“流感疾病難以預(yù)測，該研究在這方面取得了新突破。如今我們可以說，針對任何特定的潛在大型流感病毒，你可以預(yù)測哪個年齡群體很可能不治身亡，哪個年齡群體將得到保護(hù)�！�
The age effect is seen because influenza A viruses - the kind considered most likely to cause pandemics - have evolved into two major branches known as type 1 and type 2 flus.
年齡效應(yīng)可見于甲型流感病毒中。這是一種最可能廣泛傳播的流感病毒，已經(jīng)演變出甲1型流感病毒、甲2型流感病毒兩個主要分支。
Up until 1968 all viruses in circulation belonged to the type 1 branch; between 1968 and 1979, type 2 dominated. Since then, strains belonging to both branches have been in circulation simultaneously, but with one type tending to dominate each year. "It's like an oak tree that has a trunk that splits into two major branches and 1968 becomes this really clear dividing line," said Worobey.
1986年以前傳播的所有流感病毒都屬于甲1型，1968年至1979年間主要傳播的是甲2流感病毒。此后，兩種類型的流感病毒同時(shí)傳播，但是每年有一種類型會占據(jù)主導(dǎo)地位�！斑@就像是橡樹的主干長出兩個主要分枝，1968年是清晰的分界線�！�
Using vast databases of historical epidemiological data, the scientists tracked the susceptibility of each birth year from 1918 to the present to the different flus in circulation during their lifetime.
科學(xué)家們運(yùn)用流行病學(xué)歷史數(shù)據(jù)的龐大數(shù)據(jù)庫，追蹤從1918年至今每一年出生的人群對一生中所遇到的不同流感的易感程度。
The findings, published in the journal Science, showed that the strains in circulation early in life - most people have had flu by the age of five - have a profound impact on which types of flu they would be more sensitive to in the future.
該研究發(fā)表在《科學(xué)》雜志上，結(jié)果顯示（大多數(shù)人五歲前得過流感）在人們兒時(shí)傳播的流感很大程度影響了他們未來對哪類流感更為敏感。
"The (first virus you encounter) seems to set you up for life to be quite good at protecting yourself, not just against that particular virus, but also close cousins of that virus," said Worobey.
伍羅貝稱，“你感染的第一種流感病毒似乎不僅能使你對其終身免疫，也能抵御其他類似病毒�！�
The scientists also studied two bird flu viruses, H5N1 (belonging to the type 1 branch) and H7N9 (type 2), each of which already has caused hundreds of cases of severe illness or death in humans. Scientists are concerned that in the future either of these strains could gain mutations that allow them to not only jump from birds into humans, but also spread rapidly between people, triggering a deadly pandemic.
科學(xué)家們對H5N1型（屬于1型分支）和H7N9型（2型）禽流感病毒進(jìn)行了研究，目前已有數(shù)百人因此患重病或死亡�？茖W(xué)家們擔(dān)心，這類病菌未來可能發(fā)生突變，不僅能通過禽類傳染給人類還可在人類之間迅速傳播，導(dǎo)致致命流感大面積傳播。
They found that if a person's first flu infection belonged to the same branch as the avian strain, they had a 75% reduced chance of hospitalisation and about an 85% smaller chance of dying.
研究發(fā)現(xiàn)，如果一個人首次感染的流感病毒與禽流感病毒同屬一個分支，那么他們住院治療的幾率能減少75%，且死亡幾率減少85%。
The findings explain the surprising observation that H5N1 tends to cause far more mortalities in younger people - contrary to what might be expected, while H7N9 tends to be most devastating in the elderly population.
研究結(jié)果說明，H5N1病毒在年輕人中的致死率更高，這一驚人發(fā)現(xiàn)與人們的預(yù)測恰恰相反，而H7N9病毒通常對老年人殺傷力更強(qiáng)。
"We're not a completely blank slate when it comes to how susceptible we are to these emerging flu viruses," said Worobey. "Even if we've never been exposed to H5 or H7 viruses, we have some kick-ass protection against one or the other."
“我們對這些新興流感病毒并非完全沒有抵抗力。即使從沒有接觸過H5或H7型流感病毒，我們也對其中一種有強(qiáng)大的抵抗力�！�
This happens, he said, because when a person is infected by flu, their original antibodies are woken up as the body's first line of defence, meaning if they are poorly-matched they will be less efficient at attacking the virus.
他說，之所以會這樣是因?yàn)楫?dāng)人們感染流感時(shí)，其原始抗體作為身體的第一道防線會被喚醒，這意味著如果抗體與病毒不匹配，那么對病毒的攻擊便不太有效。
Previously, people had put these patterns down to younger people being more likely to encounter birds, or the virus being more aggressive in elderly people.
過去人們認(rèn)為，發(fā)生上述模式是因?yàn)槟贻p人更容易感染禽流感，或禽流病毒對老年人的攻擊力更強(qiáng)。
The scientists said it was not yet clear whether current childhood flu vaccines - which tend to involve components from both branches - would mean in future children would have higher protection against flus of both types.
科學(xué)家們稱，尚不清楚當(dāng)下常包含兩種流感病毒免疫成分的兒童流感疫苗是否意味著孩子們將來對兩種類型的流感具有較強(qiáng)的抵抗力。
Vocabulary
pandemic:(疾病)流行性的；傳染于(全國、全洲、全世界)的susceptible: 易受感染的
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