Department of Hygiene and Zoonosis, Faculty of Veterinary Medicine, University of Sadat City, Menofia, Sadat City, 32897, Egypt.
College of Agriculture, Environment and Nutrition Sciences, Tuskegee University, Tuskegee, AL, USA.
BMC Vet Res. 2022 May 12;18(1):174. doi: 10.1186/s12917-022-03273-w.
In Egypt, the highly pathogenic avian influenza (HPAI) subtype H5N1 is endemic and possesses a severe impact on the poultry. To provide a better understanding of the distributional characteristics of HPAI H5N1 outbreaks in Egypt, this study aimed to explore the spatiotemporal pattern and identify clusters of HPAI H5N1 outbreaks in Egypt from 2006 to 2017.
The Epidemic curve (EC) was constructed through time series analysis; in which six epidemic waves (EWs) were revealed. Outbreaks mainly started in winter peaked in March and ended in summer. However, newly emerged thermostable clades (2.2.1.1 and 2.2.1.2) during the 4th EW enabled the virus to survive and cause infection in warmer months with a clear alteration in the seasonality of the epidemic cycle in the 5th EW. The endemic situation became more complicated by the emergence of new serotypes. As a result, the EC ended up without any specific pattern since the 6th EW to now. The spatial analysis showed that the highest outbreak density was recorded in the Nile Delta considering it as the 'Hot spot' region. By the 6th EW, the outbreak extended to include the Nile valley. From spatiotemporal cluster epidemics, clustering in the Delta was a common feature in all EWs with primary clusters consistently detected in the hot-spot region, but the location and size varied with each EW. The highest Relative Risk (RR) regions in an EW were noticed to contain the primary clusters of the next EW and were found to include stopover sites for migratory wild birds. They were in Fayoum, Dakahlia, Qalyobiya, Sharkia, Kafr_Elsheikh, Giza, Behera, Menia, and BeniSuef governorates. Transmission of HPAI H5N1 occurred from one location to another directly resulted in a series of outbreaks forming neighboring secondary clusters. The absence of geographical borders between the governorates in addition to non-restricted movements of poultry and low vaccination and surveillance coverage contributed to the wider spread of infection all over Egypt and to look like one epidemiological unit.
Our findings can help in better understanding of the characteristics of HPAI H5N1 outbreaks and the distribution of outbreak risk, which can be used for effective disease control strategies.
在埃及，高致病性禽流感（HPAI）亚型 H5N1 是地方性的，对家禽业造成严重影响。为了更好地了解埃及 HPAI H5N1 疫情的分布特征，本研究旨在探讨 2006 年至 2017 年埃及 HPAI H5N1 疫情的时空模式，并确定疫情聚集区。
通过时间序列分析构建了流行曲线（EC），揭示了六个流行波（EW）。疫情主要在冬季开始，在 3 月达到高峰，在夏季结束。然而，第四波疫情中出现的新耐热分支（2.2.1.1 和 2.2.1.2）使病毒能够在温暖的月份存活并引起感染，从而改变了第五波疫情的季节性流行周期。新血清型的出现使疫情形势更加复杂。因此，自第六波疫情以来，EC 一直没有呈现出任何特定模式。空间分析表明，尼罗河三角洲的疫情密度最高，被认为是“热点”地区。到第六波疫情时，疫情已蔓延至尼罗河河谷。通过时空聚类疫情分析，三角洲地区的聚类是所有 EW 的共同特征，在热点地区始终检测到主要聚类，但每个 EW 的位置和大小都有所不同。在一个 EW 中，最高的相对风险（RR）区域被注意到包含下一个 EW 的主要聚类，并且发现包含候鸟的停留点。这些地区位于法尤姆、达卡利亚、盖勒尤比耶、沙基亚、卡夫尔谢赫、吉萨、贝尼苏韦夫省。HPAI H5N1 的传播是从一个地点直接传播到另一个地点，导致一系列疫情形成相邻的二级聚类。由于各省之间没有地理边界，以及家禽的自由流动和低疫苗接种率和监测覆盖率，感染在埃及各地的传播更加广泛，看起来像一个单一的流行病学单位。
我们的研究结果有助于更好地了解 HPAI H5N1 疫情的特征和疫情风险的分布，可用于制定有效的疾病控制策略。
