Risk Distribution of Human Infections with Avian Influenza H7N9 and H5N1 virus in China

Xin-Lou Li,Mai-Juan Ma,Yang Yang,Hong-Wu Yao,Ruo-Xi Sun,Wu-Chun Cao,Ye Sun,Wan-Jun Chen,Gregory C Gray,Li-Qun Fang,Kun Liu,Song Liang

doi:10.1038/srep18610

Xin-Lou Li, Mai-Juan Ma + Show 10 more

Open Access

https://doi.org/10.1038/srep18610

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Abstract

It has been documented that the epidemiological characteristics of human infections with H7N9 differ significantly between H5N1. However, potential factors that may explain the different spatial distributions remain unexplored. We use boosted regression tree (BRT) models to explore the association of agro-ecological, environmental and meteorological variables with the occurrence of human cases of H7N9 and H5N1, and map the probabilities of occurrence of human cases. Live poultry markets, density of human, coverage of built-up land, relative humidity and precipitation were significant predictors for both. In addition, density of poultry, coverage of shrub and temperature played important roles for human H7N9 infection, whereas human H5N1 infection was associated with coverage of forest and water body. Based on the risks and distribution of ecological characteristics which may facilitate the circulation of the two viruses, we found Yangtze River Delta and Pearl River Delta, along with a few spots on the southeast coastline, to be the high risk areas for H7N9 and H5N1. Additional, H5N1 risk spots were identified in eastern Sichuan and southern Yunnan Provinces. Surveillance of the two viruses needs to be enhanced in these high risk areas to reduce the risk of future epidemics of avian influenza in China.

Highlights

Global concerns regarding the possibility of an avian influenza pandemic have been accumulating since human infection with avian influenza A (H5N1) was first reported in 1997
By the end of 2014, a total of 478 avian influenza A (H7N9) and 47 A (H5N1) laboratory-confirmed human cases have been reported in mainland China
The density of poultry, the percentage coverage of shrub and temperature played important roles in the occurrence of human infection with H7N9 (BRT mean weights are 5.27%, 5.11%, and 5.17%, respectively), while the presence of human H5N1 infection was significantly associated with the percentage coverage of forest and the percentage coverage of water body (BRT mean weights are 5.51% and 5.68% respectively) (Table 1)

Summary

Introduction

Global concerns regarding the possibility of an avian influenza pandemic have been accumulating since human infection with avian influenza A (H5N1) was first reported in 1997. Recently reported human infections with novel reassortant of avian influenza A H10N8 virus and H5N6 virus, as well as a recent outbreak of H5N2 virus in poultry in China, further highlight the ongoing reassortment among avian influenza viruses[4–6]. Serological studies have suggested co-infections of H7N9 and H5N1 among herons in southern China, indicating the potential of reassortment between the two viruses[11]. It remains unclear what factors have contributed to the heterogeneity in the spatial distribution of human infections between H7N9 and H5N1. Our study aims to quantify the relative contributions of agro-ecological, environmental and meteorological factors to human H7N9 and H5N1 infections in China, and to map the high risk areas for the occurrence and concurrence of the two viruses

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