The aim of this study was to describe the spatiotemporal distribution of H5 HPAI outbreak reports for the period 2014-2017 and to identify factors associated with H5 HPAI outbreak reports. Throughout the study period, a total of 139 outbreaks of H5 HPAI in poultry were reported, due to either H5N1 (96 outbreaks) or H5N6 (43 outbreaks) subtype viruses. H5N1 HPAI outbreaks occurred in all areas of Vietnam while H5N6 HPAI outbreaks were only reported in the northern and central provinces. We counted the number of H5N1 and H5N6 outbreak report-positive districts per province over the four-year study period and calculated the provincial-level standardized morbidity ratio for H5N1 and H5N6 outbreak reports as the observed number of positive districts divided by the expected number. A mixed-effects, zero-inflated Poisson regression model was developed to identify risk factors for outbreak reports of each H5N1 and H5N6 subtype virus. Spatially correlated and uncorrelated random effects terms were included in this model to identify areas of the country where outbreak reports occurred after known risk factors had been accounted-for. The presence of an outbreak report in a province in the previous 6-12 months increased the provincial level H5N1 outbreak report risk by a factor of 2.42 (95% Bayesian credible interval [CrI] 1.27-4.60) while 1000 bird increases in the density of chickens decreased provincial level H5N6 outbreak report risk by a factor of 0.65 (95% CrI 0.38 to 0.97). We document distinctly different patterns in the spatial and temporal distribution of H5N1 and H5N6 outbreak reports. Most of the variation in H5N1 report risk was accounted-for by the fixed effects included in the zero-inflated Poisson model. In contrast, the amount of unaccounted-for risk in the H5N6 model was substantially greater than the H5N1 model. For H5N6 we recommend that targeted investigations should be carried out in provinces with relatively large spatially correlated random effect terms to identify likely determinants of disease. Similarly, investigations should be carried out in provinces with relatively low spatially correlated random effect terms to identify protective factors for disease and/or reasons for failure to report.

中文翻译：

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2014-2017年越南H5高致病性禽流感的时空和风险分析。

这项研究的目的是描述2014-2017年期间H5 HPAI爆发报告的时空分布，并确定与H5 HPAI爆发报告相关的因素。在整个研究期间，由于H5N1（96次暴发）或H5N6（43次暴发）亚型病毒，总共报告了139次禽类H5 HPAI暴发。H5N1高致病性禽流感暴发在越南所有地区发生，而H5N6高致病性禽流感暴发仅在北部和中部省份报告。我们在四年研究期内计算了每个省的H5N1和H5N6暴发报告阳性区数，并计算了省级H5N1和H5N6暴发报告的标准化发病率，即观察到的阳性区数除以预期数。混合效果 开发了零膨胀的Poisson回归模型，以识别每种H5N1和H5N6亚型病毒爆发报告的危险因素。在模型中包括空间相关和不相关的随机效应项，以识别考虑了已知风险因素后爆发报告的国家区域。在过去6至12个月内某个省中存在爆发报告，使省级H5N1爆发报告风险增加了2.42倍（95％贝叶斯可信区间[CrI] 1.27-4.60），而1000只禽的密度增加了鸡将省级H5N6爆发报告风险降低了0.65倍（95％CrI为0.38至0.97）。我们在H5N1和H5N6爆发报告的时空分布中记录了截然不同的模式。H5N1报告风险的大多数变化是由零膨胀泊松模型中包含的固定效应引起的。相比之下，H5N6模型中的无法解释的风险量明显大于H5N1模型。对于H5N6，我们建议在具有较大空间相关随机效应项的省份中进行有针对性的调查，以识别可能的疾病决定因素。同样，应在空间相关随机效应项相对较低的省份进行调查，以识别疾病的保护因素和/或未能报告的原因。对于H5N6，我们建议在具有较大空间相关随机效应项的省份中进行有针对性的调查，以识别可能的疾病决定因素。同样，应在空间相关随机效应项相对较低的省份进行调查，以识别疾病的保护因素和/或未能报告的原因。对于H5N6，我们建议在具有较大空间相关随机效应项的省份中进行有针对性的调查，以识别可能的疾病决定因素。同样，应在空间相关随机效应项相对较低的省份进行调查，以识别疾病的保护因素和/或未能报告的原因。