zh-cn	问：为什么确定新冠肺炎病毒中间宿主这么难？ 
en-us	Q: Why is it difficult to identify the intermediate host(s) of COVID-19 virus? 

zh-cn	答：病毒作为一种非细胞型微生物，无法独立生长和复制，只能在其他生物的活细胞内进行自我复制。
en-us	A: A virus, as a non-cellular microorganism, can only survive and replicate itself in living cells of other organisms. 

zh-cn	根据病毒的传播途径，一般把宿主划分为自然宿主、中间宿主和最终宿主。
en-us	Such organisms can generally be categorized into reservoir, intermediate host and final host basing on virus’ transmission routes. 

zh-cn	《中国——世界卫生组织新型冠状病毒肺炎（COVID-19）联合考察报告》中指出，新冠肺炎病毒是一种动物源性病毒，蝙蝠似乎是该病毒的自然宿主，最终宿主是人类。
en-us	The report of WHO-China Joint Mission on Coronavirus Disease 2019 (COVID-19) states that the virus that caused COVID-19 is zoonotic and that bats appear to be the reservoir and human is the final host. 

zh-cn	但是，当前确定中间宿主仍有很大困难。 
en-us	However, there are still many difficulties in identifying intermediate host(s). 

zh-cn	一是病毒溯源缺少直接证据。
en-us	First, there is no direct evidence for source tracing. 

zh-cn	本次疫情早期，中国的新冠肺炎病毒溯源工作主要聚焦于武汉华南海鲜市场。
en-us	China found an infection source from Wuhan Huanan Wholesale Seafood Market in the early stage of the outbreak. 

zh-cn	1月26日，中国疾控中心根据在华南海鲜市场提取的样本分析结果，提示该病毒可能来源于华南海鲜市场销售的野生动物。
en-us	On January 26, the Chinese Center for Disease Control and Prevention (CCDC), based on its analysis of the samples taken from the seafood market, reported that the virus appears to diffuse from wildlife species sold at the market. 

zh-cn	但是早在1月1日，华南海鲜市场就休市并进行了彻底的环境整治，市场的监控视频已无法调出，难以确定非法售卖了哪些动物。
en-us	However, the market had been shut down and cleaned up from January 1 and the surveillance video record was no longer available. Therefore, it is difficult to uncover the species. 

zh-cn	1月29日，中国疾控中心在《新英格兰医学杂志》上发表的论文显示，最早发现的病例并没有华南海鲜市场的接触史，这就不能排除病毒有其他来源的可能。
en-us	On January 29, a paper published by CCDC in The New England Journal of Medicine stated that the earliest cases had no reported link to the seafood market, and thus the possibility of other sources could not be ruled out. 

zh-cn	总之，缺少初始病例接触动物种类的直接证据，也就难以迅速锁定携带该病毒的动物。 
en-us	In short, the lack of animal contact evidence in the early cases makes it difficult to identify the intermediate host(s) directly. 

zh-cn	二是大规模筛查野生动物耗费时间。
en-us	Second, large-scale screening of wildlife is time consuming. 

zh-cn	在缺少直接证据的情况下，最可行的办法是大规模筛查野生动物。
en-us	In the absence of direct evidence, the most feasible approach is to screen wild animals on a large scale. 

zh-cn	从疫情爆发开始，已有多个研究团队指出，水貂、穿山甲、龟类都有可能是将新冠肺炎病毒传播给人类的中间宿主。
en-us	Since the outbreak of COVID-19, several research teams have pointed out that mink, pangolin, and tortoises may be the intermediate hosts . 

zh-cn	然而理论上中间宿主可以是任何动物，因此要分析的样本数量非常庞大，逐个动物对比、分析，要花大量时间和精力，这就使得溯源工作没办法迅速完成。
en-us	However, all animals are suspicious in theory, so the number of samples to be analyzed is very large, which makes the work impossible to complete in a short time.