茲卡病毒大流行拉響全球變暖的警報
2015年，全球出現(xiàn)了涉及嬰兒畸形的公共衛(wèi)生緊急情況。這一年也是有歷史記錄以來最熱的一年。這種由喜熱的蚊子所傳播的疾病在巴西爆發(fā)，是否可能只是巧合?
Scientists say it will take them years to figure that out, and pointed to other factors that mayhave played a larger role in starting the crisis. But these same experts added that the Zikaepidemic, as well as the related spread of a disease called dengue that is sickening as manyas 100 million people a year and killing thousands, should be interpreted as warnings.
科學(xué)家稱，要確定是否屬于巧合需要進行多年的研究。他們指出這次危機可能另有原因。但是，這些專家還補充說，茲卡的疫情以及與之相關(guān)的登革熱的傳播應(yīng)該被視為一種警告。后者一年最多能感染1億人，并造成數(shù)以千計的人們死亡。
Over the coming decades, global warming is likely to increase the range and speed the lifecycle of the particular mosquitoes carrying these viruses, encouraging their spread deeperinto temperate countries like the United States.
在未來幾十年，全球變暖可能造成那些攜帶這些病毒的特殊種類的蚊子的活動范圍擴大和生命周期加快，進而促使這些疫病向美國等溫帶國家擴展。
Recent research suggests that under a worst-case scenario, involving continued high globalemissions coupled with fast population growth, the number of people exposed to the principalmosquito could more than double, to as many as 8 billion or 9 billion by late this century fromroughly 4 billion today.
近期的研究表明，最糟糕的一種情況是，隨著全球溫室氣體的大量排放和人口的高速增長，有可能接觸這種蚊子的人口將翻番，目前是40億左右，到本世紀(jì)末將多達80億或90億。
“As we get continued warming, it’s going to become more difficult to control mosquitoes,” saidAndrew Monaghan, who is studying the interaction of climate and health at the NationalCenter for Atmospheric Research in Boulder, Colo. “The warmer it is, the faster they candevelop from egg to adult, and the faster they can incubate viruses.”
“隨著全球變暖，控制蚊子將越來越困難。”安德魯·莫納甘(Andrew Monaghan)說。安德魯在科羅拉多州博爾德的美國國家大氣研究中心(National Center for Atmospheric Research)研究氣候與健康的互動關(guān)系。“天氣越熱，蚊子從孵化到成年的速度就越快，病毒繁殖的速度也就越快。”
Already, climate change is suspected — though not proven — to have been a factor in a stringof disease outbreaks afflicting both people and animals. These include the spread of malariainto the highlands of eastern Africa, the rising incidence of Lyme disease in North America,and the spread of a serious livestock ailment called bluetongue into parts of Europe that wereonce too cold for it to thrive.
人們懷疑，氣候變化是人畜感染一系列疾病的一個原因，盡管這一點尚未得到證實。這些疾病包括東非高原地區(qū)的瘧疾，北美萊姆病的發(fā)病率升高，歐洲部分地區(qū)的牲畜出現(xiàn)的嚴(yán)重的藍(lán)舌病疫情，那些地區(qū)之前因為太冷，很少出現(xiàn)這些疾病。
In interviews, experts noted that no epidemic was ever the result of a single variable.
在訪談中，專家指出沒有任何一種傳染病是僅由一個變量引起的。
Instead, epidemics always involve interactions among genes, ecology, climate and humanbehavior, presenting profound difficulties for scientists trying to tease apart the contributingfactors. “The complexity is enormous,” said Walter J. Tabachnick, a professor with the FloridaMedical Entomology Laboratory, a unit of the University of Florida in Vero Beach.
相反，傳染病常常涉及基因、生態(tài)、氣候、人類行為等多種因素的互動，所以科學(xué)家很難把單個因素分離出來。“原因極為復(fù)雜。”佛羅里達大學(xué)(University of Florida)位于維羅比奇(Vero Beach)的佛羅里達醫(yī)學(xué)昆蟲學(xué)實驗室的教授瓦爾特·塔巴奇尼克(Walter J. Tabachnick)說。
The epidemics of Zika and dengue are cases in point. The viruses are being transmitted largelyby the yellow fever mosquito, Aedes aegypti. That creature adapted long ago to live in humansettlements, and developed a concomitant taste for human blood.
茲卡和登革熱就是典型的例子。這些病毒主要是由感染黃熱病的伊蚊傳播。這種生物早已適應(yīng)了在人類聚居地生存，并因此喜好人類的血液。
Cities in the tropics, the climate zone most favorable to the mosquito, have undergoneexplosive growth: Humanity passed a milestone a few years ago when more than half thepopulation had moved to urban areas. But spending on health care and on basic public healthinfrastructure, like water pipes and sewers, has not kept pace. Mosquito control has alsofaltered in recent decades.
熱帶是最適合蚊子生存的氣候帶，而那里的城市正在經(jīng)歷迅猛的增長：幾年前人類就跨過了一個里程碑：一半以上的人口已遷居到城市地區(qū)。但是公共醫(yī)療和公共衛(wèi)生基礎(chǔ)設(shè)施的投入，比如水管和下水設(shè)施，仍是滯后的。近幾十年對蚊子的控制也出現(xiàn)了放松。
The mosquito lays its eggs in containers of water, of a sort that are especially common in thehuge slums of Latin American cities. With unreliable access to piped water, people there storewater in rooftop cisterns, buckets and the like. Old tires and other debris can also becomemosquito habitat.
蚊子在盛水的容器中產(chǎn)卵，這種容器在拉丁美洲城市的大型貧民窟中尤其常見。由于沒有可靠的管道用水，那里的人們會把水存放在屋頂?shù)乃?、水桶和類似的容器中。舊輪胎和其他垃圾也可能成為蚊子的棲息地。
Water storage near homes is commonplace in areas where Zika has spread rapidly, like thecities of Recife and Salvador in northeastern Brazil, and where dengue experienced a surge in2015, like S漀 Paulo, Brazil’s largest state.
在茲卡病毒迅速傳播的區(qū)域，比如巴西東北部城市累西腓和薩爾瓦多，以及2015年出現(xiàn)登革熱病例激增的巴西最大州圣保羅，都有在民宅附近存水的習(xí)慣。
Altogether, dengue killed at least 839 people in Brazil in 2015, a 40 percent increase from theprevious year. Worldwide, dengue is killing more than 20,000 people a year.
2015年，巴西共有至少839人死于登革熱，比上一年增加40%。而全世界一年有超過2萬人死于登革熱。 多名專家在訪談中稱，疾病爆發(fā)的一個主要原因很可能是城市化、人口增長和跨國旅行造成受風(fēng)險人口增加。他們認(rèn)為氣候變化只是壓垮駱駝的最后一根稻草。
Several experts said in interviews that a main reason for the disease outbreaks was most likelythe expansion of the number of people at risk, through urbanization, population growth andinternational travel. They see the changing climate as just another stress on top of a situationthat was already rife with peril.
多名專家在采訪中說，疾病爆發(fā)的一個主要原因很可能是隨著城市化、人口增長和跨國旅行，面臨風(fēng)險的人群擴大了。他們認(rèn)為在已經(jīng)有重重危險的局面中，氣候變化只是其中的一重壓力。
While they do not understand to what degree rising temperatures and other weather shiftsmay have contributed to the outbreaks, they do understand some of the potentialmechanisms.
雖然他們并不知道氣溫升高和其他氣候變化因素，對疫情爆發(fā)的作用有多大，但是他們明白其中一些潛在的機制。
The mosquitoes mostly live on flower nectar, but the female of the species needs a meal ofhuman blood to have enough protein to lay her eggs. If she bites a person infected withdengue, Zika or any of several other diseases, she picks up the virus.
蚊子大多以花蜜為生，但是雌性蚊子為了產(chǎn)卵，需要吸人血來提供充足的蛋白質(zhì)。如果它叮了已感染登革熱、茲卡或其他幾種病的人，它就攜帶了該種病毒。
The virus has to reproduce in the mosquito for a certain period before it can be transmittedto another person in a subsequent bite. The higher the air temperature, the shorter thatincubation period. Moreover, up to a point, higher temperatures cause the mosquitoes tomature faster.
病毒需要在蚊子的體內(nèi)繁殖一段時間，才能在下一次叮咬時傳播給他人。溫度越高，病毒繁殖所需的時間就越短。而且在某個限度以內(nèi)，溫度越高，蚊子的成熟就越快。
With rising temperatures, “You’re actually speeding up the whole reproductive cycle of themosquitoes,” said Charles B. Beard, who heads a unit in Fort Collins, Colo., studying insect-borne diseases for the Centers for Disease Control and Prevention in Atlanta. “You get largerpopulations, with more generations of mosquitoes, in a warmer, wetter climate. You have thiskind of amplification of the risk.”
溫度上升“實際上會加速蚊子的整個繁殖周期，”查爾斯·B·彼爾德(Charles B. Beard)說，“人口增加了，在更潮濕、更炎熱的氣候里，存活的蚊子世代也增多了，這就放大了風(fēng)險。”彼爾德領(lǐng)導(dǎo)著一個位于科羅拉多州科林斯堡的團隊，為亞特蘭大的疾病控制與預(yù)防中心(Centers for Disease Control and Prevention inAtlanta)進行昆蟲傳播疾病研究。
In principle, the risk from continued global warming applies not just to temperate countries,but to cities at high altitude in tropical countries. Researchers are keeping a close eye onMexico City, for instance.
理論上，全球持續(xù)變暖所帶來的風(fēng)險，不僅涉及溫帶國家，還涉及熱帶國家的高海拔城市。比如，研究人員正在密切關(guān)注墨西哥城。
With 21 million people in the city and its suburbs, Mexico City is the largest metropolis of theWestern Hemisphere. While the lowlands of Mexico are plagued by yellow fever mosquitoesand the viruses they transmit, the country’s capital sits on a mountain plain that has — up tonow — been too cold for the mosquitoes.
墨西哥城的城區(qū)和郊區(qū)一共有2100萬人，它是西半球最大的都市。雖然在墨西哥的低地，感染黃熱病和其他病毒的蚊子到處肆虐，但是墨西哥的首都位于較寒冷的山頂平原，至少目前蚊子還無法在那里生存。
But temperatures are rising, and the mosquitoes have recently been detected in low numbersnear Mexico City.
但是隨著氣溫的升高，墨西哥城附近最近發(fā)現(xiàn)了少量的蚊子。
“The mosquito is just down the hill, literally,” Dr. Monaghan said. “I think all the potential isthere to have virus transmission if climatic conditions become a bit more suitable.”
“蚊子已經(jīng)來到山腳下了，”莫納甘博士說。“我覺得只要氣候條件再合適一點，病毒就有可能開始傳播。”
