Veterinary Epidemiology, Economics and Public Health Group, Department of Production and Population Health, Royal Veterinary College, University of London, Hatfield AL9 7TA, United Kingdom.
Proc Natl Acad Sci U S A. 2013 May 28;110(22):9177-82. doi: 10.1073/pnas.1220815110. Epub 2013 May 6.
Highly pathogenic avian influenza virus subtype H5N1 is endemic in Asia, with live bird trade as a major disease transmission pathway. A cross-sectional survey was undertaken in northern Vietnam to investigate the structure of the live bird market (LBM) contact network and the implications for virus spread. Based on the movements of traders between LBMs, weighted and directed networks were constructed and used for social network analysis and individual-based modeling. Most LBMs were connected to one another, suggesting that the LBM network may support large-scale disease spread. Because of cross-border trade, it also may promote transboundary virus circulation. However, opportunities for disease control do exist. The implementation of thorough, daily disinfection of the market environment as well as of traders' vehicles and equipment in only a small number of hubs can disconnect the network dramatically, preventing disease spread. These targeted interventions would be an effective alternative to the current policy of a complete ban of LBMs in some areas. Some LBMs that have been banned still are very active, and they likely have a substantial impact on disease dynamics, exhibiting the highest levels of susceptibility and infectiousness. The number of trader visits to markets, information that can be collected quickly and easily, may be used to identify LBMs suitable for implementing interventions. This would not require prior knowledge of the force of infection, for which laboratory-confirmed surveillance would be necessary. These findings are of particular relevance for policy development in resource-scarce settings.
高致病性禽流感病毒 H5N1 亚型在亚洲流行，活禽交易是主要的疾病传播途径。在越南北部进行了一项横断面调查，以研究活禽市场（LBM）接触网络的结构及其对病毒传播的影响。基于贸易商在 LBM 之间的流动情况，构建了加权和有向网络，并用于社交网络分析和个体建模。大多数 LBM 相互连接，这表明 LBM 网络可能支持大规模疾病传播。由于跨境贸易，它也可能促进跨境病毒循环。然而，确实存在疾病控制的机会。彻底、每日对市场环境以及贸易商车辆和设备进行消毒，在少数几个中心实施，就可以显著断开网络，防止疾病传播。与某些地区目前完全禁止 LBM 的政策相比，这些有针对性的干预措施将是一种有效的替代方案。一些已被禁止的 LBM 仍然非常活跃，它们可能对疾病动态产生重大影响，表现出最高的易感性和传染性。贸易商访问市场的次数，这些信息可以快速、轻松地收集，可以用来确定适合实施干预措施的 LBM。这不需要事先了解感染力度，因为这需要实验室确认监测。这些发现对于资源匮乏环境中的政策制定具有特别重要的意义。
