农业部和世界动物卫生组织（OIE）联合考察组通过对H7N9疫情的调查表明，目前人感染H7N9的风险主要来自活禽市场环境。然而，发表在《自然》网站的专栏文章也曾指出，这种新病毒可能已在野生鸟类中传播，并且已有相关证据表明，鸟类迁徙在禽流感病毒的传播中起着至关重要的作用。作为禽流感病毒的天然宿主，许多候鸟在迁徙过程中会在相同的栖息地或停歇地停留，在此过程中，禽流感病毒可能通过受鸟类粪便污染的地表水等途径进行传播。有鉴于此，近期发表在国际期刊Infectious Diseases of Poverty上的文章Identifying key bird species and geographical hotspots of avian influenza A (H7N9) virus in China，系统研究和评估了与禽流感时空传播相关的关键鸟种，并绘制了其时空分布及热点地区。
In China since the first human infection of avian influenza A (H7N9) virus was identified in 2013, it has caused serious public health concerns due to its wide spread and high mortality rate. Evidence shows that bird migration plays an essential role in global spread of avian influenza viruses. Accordingly, in this paper, we aim to identify key bird species and geographical hotspots that are relevant to the transmission of avian influenza A (H7N9) virus in China.
Methods
We first conducted phylogenetic analysis on 626 viral sequences of avian influenza A (H7N9) virus isolated in chicken, which were collected from the Global Initiative on Sharing All Influenza Data (GISAID), to reveal geographical spread and molecular evolution of the virus in China. Then, we adopted the cross correlation function (CCF) to explore the relationship between the identified influenza A (H7N9) cases and the spatiotemporal distribution of migratory birds. Here, the spatiotemporal distribution of bird species was generated based on bird observation data collected from China Bird Reports, which consists of 157 272 observation records about 1145 bird species. Finally, we employed a kernel density estimator to identify geographical hotspots of bird habitat/stopover that are relevant to the influenza A (H7N9) infections.
Results
Phylogenetic analysis reveals the evolutionary and geographical patterns of influenza A (H7N9) infections, where cases in the same or nearby municipality/provinces are clustered together with small evolutionary differences. Moreover, three epidemic waves in chicken along the East Asian–Australasian flyway in China are distinguished from the phylogenetic tree. The CCF analysis identifies possible migratory bird species that are relevant to the influenza A(H7N9) infections in Shanghai, Jiangsu, Zhejiang, Fujian, Jiangxi, and Guangdong in China, where the six municipality/provinces account for 91.2% of the total number of isolated H7N9 cases in chicken in GISAID. Based on the spatial distribution of identified bird species, geographical hotspots are further estimated and illustrated within these typical municipality/provinces.
Conclusions
In this paper, we have identified key bird species and geographical hotspots that are relevant to the spread of influenza A (H7N9) virus. The results and findings could provide sentinel signal and evidence for active surveillance, as well as strategic control of influenza A (H7N9) transmission in China.
Infectious Diseases of Poverty (https://idpjournal.biomedcentral.com/, 2.708 - 2-year Impact Factor, 3.126 - 5-year Impact Factor) is an open access, peer-reviewed journal publishing topic areas and methods that address essential public health questions relating to infectious diseases of poverty. These include various aspects of the biology of pathogens and vectors, diagnosis and detection, treatment and case management, epidemiology and modeling, zoonotic hosts and animal reservoirs, control strategies and implementation, new technologies and application. Transdisciplinary or multisectoral effects on health systems, ecohealth, environmental management, and innovative technology are also considered.
