上海交大赵大海做客东方卫视演播室：西安市封控和全民核酸检测是适宜的防控措施
上海交通大学国际与公共事务学院教授、博士生导师，上海交通大学-耶鲁大学卫生政策联合研究中心执行主任赵大海，自新冠肺炎疫情暴发以来，对于新冠疫情暴发、防控以及卫生政策第49次接受上海电视台专访，也是第115次接受央视、上视专访。2021年12月28日，赵大海做客东方卫视演播室，在《今晚》节目就西安市新冠疫情暴发和防控的话题进行了解释和评论。同期嘉宾是德国杜伊斯堡埃森大学病毒研究所陆蒙吉教授，现仅将有关赵大海的访谈内容摘录如下。
主持人蒋昌建：相关话题我们在上海演播室邀请到了上海交通大学-耶鲁大学卫生政策联合研究中心执行主任赵大海。有观点指出在启动五轮全员核酸之后，西安发现病例的数量屡创新高，同时从发现核酸异常到确诊的时间也在缩短，那么这也就意味着西安捕获病毒的速度在提高，那么您怎么看这样的说法？
赵大海：我从两个方面来回答这个问题。第一，西安市确实在短时间之内做了几千万的核酸检测，应该讲西安市的核酸检测技术、临床辅助诊断技术有所提高，是能够理解的。另外一个方面，目前所发现的新增确诊病例连续三天都超过一百五十例，这些病例当中只有一部分是来自于全民核酸检测，超过一半的是来自于已封控的包括密切接触者在内的群体。应该讲，我们还不能将现在每日比较多的新增病例完全归功于核酸检测技术的提高。
主持人蒋昌建：西安疫情的源头已经确定为境外输入，但是具体的传播链条尚不清晰。近日有媒体发文宣称，西安机场空调系统的特殊结构导致了病毒传播，引发了各界的关注。接下来的问题想问一下，空调的传播到目前为止意见不统一，也只是一个猜测，那么问题就来了，西安本轮疫情有的传播链跟机场有关，有的传播链到目前为止还不太清楚，流调也给我们找到传播链本身或者是并列链来分析造成一定的难度。那么问题就是，怎么溯源？难度在哪？
赵大海：流调和溯源的困难，对于西安市的本轮疫情而言，其实最大的困难点就在于，当我们觉察到西安的新冠疫情的时候，其实疫情已经在一段时间之内发生了，也就是说我们没有做到早发现。而且当觉察到有新冠疫情的时候，其实已经存在社区传播。在新冠疫情社区传播的时候，那再通过简单的或者传统的流调，以及开展相关的溯源工作，就会非常困难。而我们能够采用的比较科学的防控策略，就是现在西安市所采用的一方面封控，另外一方面开展多轮的全市全民核酸检测。
供稿者：国务学院
日期：2021年12月29日
Dahai ZHAO’s Exclusive Interview with ShanghaiTV: Lockdown and citywide nucleic acid testing are the appropriate strategies for Xi’an’s given situation
Dahai Zhao, a doctoral supervisor at SJTU School of International and Public Affairs, the Executive Director of YALE-SJTU Joint Research Center for Health Policy, has been interviewed by ShanghaiTV for the 49th time (115times by CGTN / ShanghaiTV altogether) since the COVID-19 pandemic. On 28 November, Zhao commented on COVID containment in Xi’an on Shanghai TV.
Moderate: It is pointed out that the number of cases found in Xi 'an reached new highs after five rounds of nucleic acid were launched. Meanwhile, the time between detection of nucleic acid abnormalities and diagnosis is also shortening. This means that the rate of virus capture in Xi 'an is improving. What do you think of this statement?
ZHAO: I answer this question from two sides. First, Xi‘an has indeed done tens of millions of nucleic acid tests in a short time. Xi’an's nucleic acid detection technology and clinically assisted diagnosis technology have been improved. And the number of new confirmed cases has exceeded 150 for the third consecutive day. Only a fraction of these cases have come from population-based nucleic acid testing, and more than half have come from quarantined groups including close contacts. It should be said that we cannot fully attribute the daily increase in new cases to the improvement of nucleic acid testing technology.
Moderate: The source of the outbreak in Xi 'an has been determined to be imported from abroad, but the exact transmission chain is still unclear. Recently, some media published articles claiming that the air conditioning system at Xi’an Airport caused the spread of the virus, which has aroused concern from all circles. The spread of air conditioning so far has been inconsistent and is just a guess. Some of the transmission chains in Xi’an are related to the airport, while others remain unclear so far. This also makes it difficult to find the transmission chain itself or parallel chain to analyze through the epidemiological survey. So the question is, how do you trace it? What's the difficulty?
ZHAO: For Xi’an, the biggest difficulty is that the epidemic had already happened for a period of time when we were aware of it. That is to say, we failed to detect it early. And by the time COVID-19 is detected, there is already community transmission. When COVID is spreading in the community, it will be very difficult to carry out simple or traditional monitoring and tracing related work. The more scientific prevention and control strategy is the lockdown adopted by Xi’an on the one hand, and multiple rounds of nucleic acid testing for the whole city on the other hand.
Contributor: SIPA, SJTU
Date: December 29, 2021