>>>沪江汶川地震专题

【讨论】

长久以来，“大灾之后必有大疫”的预期对公众和决策者进行判断的影响颇深。这种被误导的预期（通常是因为人们把疾病与尸体关联起来）会导致受灾人群的担忧和恐慌，并引发媒体和其它相关机构的认知混乱。

实际上，自然灾害后疫情爆发的可能性较低，当灾害没有导致大规模的人口迁移时尤其如此。而当临时迁移人群的基本生存补给（如清洁的饮用水和卫生设施、足够的临时居所场所和基本的医疗服务）不足时，传染性疾病就很可能在人群中流行。

那些容易导致疾病传播的不利条件，应当在第一时间内通过迅速恢复基础服务的方法得到改善。确保清洁的饮水和基本医疗服务是很关键的，同样关键的还有对受灾地区易发疾病的监控和预警。

全面进行传染性疾病风险评估，可以帮我们确定哪些疾病应该优先进入监控网，并为免疫接种和疾病媒介控制工作分出轻重缓急。在附录表二里总结了灾后减缓传染病传播的五个基本步骤。灾害引起的死亡绝大多数都是由外伤恶化导致的。灾难应急预案自然应该着重关注外伤救治和伤亡人员管理，但也应该把灾后幸存者的医护需求考虑进去。

对于灾后常出现的大批幸存者聚集而缺少清洁饮用水和卫生设施的情况，我们必须在救治和预防两方面都做好充分的准备。例如清洁饮用水的快速送达，治疗脱水的药品、抗生素，以及疫苗等药品的足量供应等等。受灾地区的监控对于掌握自然灾害对当地传染病致病率、致死率的相关影响是至关重要的。然而，在灾后的环境中，获得相关的监控数据通常并非易事。在灾难中，公共基础医疗设施的损坏使原本脆弱不堪的监控和反应体系更加恶化，甚至被完全破坏。就像在 2004 年 印尼亚齐（Aceh）灾难中，监控官员和公共医疗人员本身就有可能死亡或失踪。人口迁移也可能会对普查数据造成扭曲，这使得对比数据的计算更加困难。

紧急情况下的医疗卫生服务通常由多个国家和国际组织提供，这对多方协调工作是个挑战。同时，灾前基准监控数据的缺乏，给精确判断自然灾害给疾病传播带来的冲击造成困难。

虽然灾后监控系统主要针对当下（灾后）流行疾病的快速检测，但缺少基准监控数据和精确的参考值作为分母，会对检测数据的解读造成障碍。检测到的地方性流行性疾病病例可能会被解读（由于缺少背景数据）为灾后流行疾病的趋势。然而，在这种情况下，当检测到传染性疾病的病例时，应优先考虑的是快速实施控制措施。尽管面对这些挑战和困难，对传染性疾病的持续监测以及快速反应；对于监控疾病的发生、记录它们的影响、实施必要的应急控制措施、以及更好地评估灾后疾病爆发的风险起着核心的作用。

Discussion
Historically, fears of major disease outbreaks in the aftermath of natural disasters have shaped the perceptions of the public and policymakers. These expectations, misinformed by associations of disease with dead bodies, can create fear and panic in the affected population and lead to confusion in the media and elsewhere.

The risk for outbreaks after natural disasters is low, particularly when the disaster does not result in substantial population displacement. Communicable diseases are common in displaced populations that have poor access to basic needs such as safe water and sanitation, adequate shelter, and primary healthcare services. These conditions, many favorable for disease transmission, must be addressed immediately with the rapid reinstatement of basic services. Assuring access to safe water and primary healthcare services is crucial, as are surveillance and early warning to detect epidemic-prone diseases known to occur in the disaster-affected area. A comprehensive communicable disease risk assessment can determine priority diseases for inclusion in the surveillance system and prioritize the need for immunization and vector-control campaigns. Five basic steps that can reduce the risk for communicable disease transmission in populations affected by natural disasters are summarized in an online table (Appendix Table).

Disaster-related deaths are overwhelmingly caused by the initial traumatic impact of the event. Disaster-preparedness plans, appropriately focused on trauma and mass casualty management, should also take into account the health needs of the surviving disaster-affected populations. The health effects associated with the sudden crowding of large numbers of survivors, often with inadequate access to safe water and sanitation facilities, will require planning for both therapeutic and preventive interventions, such as the rapid delivery of safe water and the provision of rehydration materials, antimicrobial agents, and measles vaccination materials.

Surveillance in areas affected by disasters is fundamental to understanding the impact of natural disasters on communicable disease illness and death. Obtaining relevant surveillance information in these contexts, however, is frequently challenging. The destruction of the preexisting public health infrastructure can aggravate (or eliminate) what may have been weak predisaster systems of surveillance and response. Surveillance officers and public health workers may be killed or missing, as in Aceh in 2004. Population displacement can distort census information, which makes the calculation of rates for comparison difficult. Healthcare during the emergency phase is often delivered by a wide range of national and international actors, which creates coordination challenges. Also, a lack of predisaster baseline surveillance information can lead to difficulties in accurately differentiating epidemic from background endemic disease transmission.

Although postdisaster surveillance systems are designed to rapidly detect cases of epidemic-prone diseases, interpreting this information can be hampered by the absence of baseline surveillance data and accurate denominator values. Detecting cases of diseases that occur endemically may be interpreted (because of absence of background data) as an early epidemic. The priority in these settings, however, is rapid implementation of control measures when cases of epidemic-prone diseases are detected. Despite these challenges, continued detection of and response to communicable diseases are essential to monitor the incidence of diseases, to document their effect, to respond with control measures when needed, and to better quantify the risk for outbreaks after disasters.