茲卡病毒大流行拉響全球變暖的警報
The global public health emergency involving deformed babies emerged in 2015, the hottest year in the historical record, with an outbreak in Brazil of a disease transmitted by heat-loving mosquitoes. Can that be a coincidence?
2015年，全球出現了涉及嬰兒畸形的公共衛生緊急情況。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，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 may have played a larger role in starting the crisis. But these same experts added that the Zika epidemic, as well as the related spread of a disease called dengue that is sickening as many as 100 million people a year and killing thousands, should be interpreted as warnings.
科學家稱，要確定是否屬於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的登革熱的傳播應該被視爲一種警告。後者一年最多能感染1億人，並造成數以千計的人們死亡。
Over the coming decades, global warming is likely to increase the range and speed the life cycle of the particular mosquitoes carrying these viruses, encouraging their spread deeper into 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範圍擴大和生命週期加快，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 global emissions coupled with fast population growth, the number of people exposed to the principal mosquito could more than double, to as many as 8 billion or 9 billion by late this century from roughly 4 billion today.
近期的研究表明，最糟糕的一種情況是，隨着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，到本世紀末將多達80億或90億。
“As we get continued warming, it’s going to become more difficult to control mosquitoes,” said Andrew Monaghan, who is studying the interaction of climate and health at the National Center for Atmospheric Research in Boulder, Colo. “The warmer it is, the faster they can develop from egg to adult, and the faster they can incubate viruses.”
“隨着全球變暖，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係。“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 string of disease outbreaks afflicting both people and animals. These include the spread of malaria into 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 were once 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，儘管這一點尚未得到證實。這些疾病包括東非高原地區的瘧疾，北美萊姆病的發病率升高，歐洲部分地區的牲畜出現的嚴重的藍舌病疫情，那些地區之前因爲太冷，很少出現這些疾病。
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 human behavior, presenting profound difficulties for scientists trying to tease apart the contributing factors. “The complexity is enormous,” said Walter J. Tabachnick, a professor with the Florida Medical 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、氣候、人類行爲等多種因素的互動，所以科學家很難把單個因素分離出來。“原因極爲複雜。”佛羅里達大學(University of Florida)位於維羅比奇(Vero Beach)的佛羅里達醫學昆蟲學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 largely by the yellow fever mosquito, Aedes aegypti. That creature adapted long ago to live in human settlements, 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。這種生物早已適應了在人類聚居地生存，並因此喜好人類的血液。
Cities in the tropics, the climate zone most favorable to the mosquito, have undergone explosive growth: Humanity passed a milestone a few years ago when more than half the population had moved to urban areas. But spending on health care and on basic public health infrastructure, like water pipes and sewers, has not kept pace. Mosquito control has also faltered in recent decades.
熱帶是最適合蚊子生存的氣候帶，而那裏的城市正在經歷迅猛的增長：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。但是公共醫療和公共衛生基礎設施的投入，比如水管和下水設施，仍是滯後的。近幾十年對蚊子的控制也出現了放鬆。
The mosquito lays its eggs in containers of water, of a sort that are especially common in the huge slums of Latin American cities. With unreliable access to piped water, people there store water in rooftop cisterns, buckets and the like. Old tires and other debris can also become mosquito habitat.
蚊子在盛水的容器中產卵，這種容器在拉丁美洲城市的大型貧民窟中尤其常見。由於沒有可靠的管道用水，那裏的人們會把水存放在屋頂的水箱、水桶和類似的容器中。舊輪胎和其他垃圾也可能成爲蚊子的棲息地。
Water storage near homes is commonplace in areas where Zika has spread rapidly, like the cities of Recife and Salvador in northeastern Brazil, and where dengue experienced a surge in 2015, like S漀 Paulo, Brazil’s largest state.
在茲卡病毒迅速傳播的區域，比如巴西東北部城市累西腓和薩爾瓦多，以及2015年出現登革熱病例激增的巴西最大州聖保羅，都有在民宅附近存水的習慣。
Altogether, dengue killed at least 839 people in Brazil in 2015, a 40 percent increase from the previous year. Worldwide, dengue is killing more than 20,000 people a year.
2015年，巴西共有至少839人死於登革熱，比上一年增加40%。而全世界一年有超過2萬人死於登革熱。 多名專家在訪談中稱，疾病爆發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險人口增加。他們認爲氣候變化只是壓垮駱駝的最後一根稻草。
Several experts said in interviews that a main reason for the disease outbreaks was most likely the expansion of the number of people at risk, through urbanization, population growth and international travel. They see the changing climate as just another stress on top of a situation that was already rife with peril.
多名專家在採訪中說，疾病爆發的一個主要原因很可能是隨着城市化、人口增長和跨國旅行，面臨風險的人羣擴大了。他們認爲在已經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 shifts may have contributed to the outbreaks, they do understand some of the potential mechanisms.
雖然他們並不知道氣溫升高和其他氣候變化因素，對疫情爆發的作用有多大，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 of human blood to have enough protein to lay her eggs. If she bites a person infected with dengue, Zika or any of several other diseases, she picks up the virus.
蚊子大多以花蜜爲生，但是雌性蚊子爲了產卵，需要吸人血來提供充足的蛋白質。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 transmitted to another person in a subsequent bite. The higher the air temperature, the shorter that incubation period. Moreover, up to a point, higher temperatures cause the mosquitoes to mature faster.
病毒需要在蚊子的體內繁殖一段時間，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，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 the mosquitoes,” 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 larger populations, with more generations of mosquitoes, in a warmer, wetter climate. You have this kind of amplification of the risk.”
溫度上升“實際上會加速蚊子的整個繁殖週期，”查爾斯·B·彼爾德(Charles B. Beard)說，“人口增加了，在更潮溼、更炎熱的氣候裏，存活的蚊子世代也增多了，這就放大了風險。”彼爾德領導着一個位於科羅拉多州科林斯堡的團隊，爲亞特蘭大的疾病控制與預防中心(Centers for Disease Control and Prevention in Atlanta)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 on Mexico City, for instance.
理論上，全球持續變暖所帶來的風險，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注墨西哥城。
With 21 million people in the city and its suburbs, Mexico City is the largest metropolis of the Western Hemisphere. While the lowlands of Mexico are plagued by yellow fever mosquitoes and the viruses they transmit, the country’s capital sits on a mountain plain that has — up to now — been too cold for the mosquitoes.
墨西哥城的城區和郊區一共有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於較寒冷的山頂平原，至少目前蚊子還無法在那裏生存。
But temperatures are rising, and the mosquitoes have recently been detected in low numbers near Mexico City.
但是隨着氣溫的升高，墨西哥城附近最近發現了少量的蚊子。
“The mosquito is just down the hill, literally,” Dr. Monaghan said. “I think all the potential is there to have virus transmission if climatic conditions become a bit more suitable.”
“蚊子已經來到山腳下了，”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。”
