Istituto Zooprofilattico Sperimentale delle Venezie-IZSVe, Viale dell'Università 10, 35020 Legnaro, Padua, Italy.
Prev Vet Med. 2010 Jul 1;95(3-4):267-74. doi: 10.1016/j.prevetmed.2010.04.005. Epub 2010 May 6.
Exposure to the risk of neighbourhood infection was estimated for the H7N1 Highly Pathogenic Avian Influenza (HPAI) epidemic that affected Northern Italy between 1999 and 2000. The two most affected regions (Lombardy and Veneto) were analyzed and the epidemic was divided into three phases. Q statistics were used to evaluate exposure to the risk of neighbourhood infection using two measures. First, a local Q statistic (Qikt) assessed daily exposure for each farm as a function of the number of neighbouring infected farms that were in their infectious period, weighted by the distance between farms. This allowed us to identify the daily time course of risk for each farm and, at any given time, local groups of farms defined by high risk. Second, for each farm a summary statistic of exposure risk within each phase (Qiph) was obtained by summing Qikt over the duration of each phase. This allowed identification of farms defined by persistent, high exposure risk within each phase of the epidemic. Statistical significance was evaluated using conditional Monte Carlo simulation, and significant values of Qiph were mapped to assess the variation of the risk of neighbourhood infection through the phases. Qikt was larger for farms in Lombardy and the reduction of exposed farms was more marked for Veneto. Although the highest value of Qiph was observed in Veneto, in each phase most of the significant values were in Lombardy. In the last phase of the epidemic, a large reduction in the number of farms significantly exposed to the risk of neighbourhood infection was observed in the Veneto region, along with generally low values of Qiph. This may be explained by differences in control measures in the two regions, including pre-emptive slaughtering of farms considered at high risk of infection. The Q statistic allowed us to quantify geographic, time-dynamic variations in exposure to neighbourhood infection, and to generate hypotheses on the efficacy of control measures.
针对 1999 年至 2000 年期间意大利北部爆发的 H7N1 高致病性禽流感（HPAI）疫情，评估了感染风险。对受影响最严重的两个地区（伦巴第和威尼托）进行了分析，并将疫情分为三个阶段。使用 Q 统计量使用两种方法评估接触邻里感染风险。首先，局部 Q 统计量（Qikt）评估了每个农场作为其感染期内感染农场数量的函数的每日暴露程度，权重为农场之间的距离。这使我们能够确定每个农场的每日风险时间过程，并且在任何给定时间，都可以根据高风险定义农场的局部群体。其次，对于每个农场，通过在每个阶段的持续时间内对 Qikt 求和，获得了每个阶段内暴露风险的摘要统计量（Qiph）。这允许识别在疫情每个阶段内持续存在高暴露风险的农场。使用条件蒙特卡罗模拟评估统计显着性，并且将显着的 Qiph 值映射到评估整个疫情阶段邻里感染风险的变化。伦巴第的农场的 Qikt 值更大，而威尼托的暴露农场数量减少更为明显。尽管在威尼托观察到 Qiph 的最高值，但在每个阶段，大部分显着值都在伦巴第。在疫情的最后阶段，威尼托地区观察到明显暴露于邻里感染风险的农场数量大量减少，同时 Qiph 值通常较低。这可能是由于两个地区的控制措施存在差异，包括对被认为处于高感染风险的农场进行先发制人的屠杀。Q 统计量使我们能够量化接触邻里感染的地理和时间动态变化，并提出有关控制措施效果的假设。
