Abstract
Descriptive and geographic information system methods were used to depict the spatial and temporal characteristics of the outbreak of human infection with a novel avian influenza A(H7N9) virus in mainland China, the peak of which appeared between 28 March and 18 April 2013. As of 31 May 2013, there was a total of 131 reported human infections in China, with a cumulative mortality of 29% (38/131). The outbreak affected 10 provinces, with 106 of the cases being concentrated in the eastern coastal provinces of Zhejiang, Shanghai and Jiangsu. Statistically significant spatial clustering of cumulative human cases was identified by the Cuzick–Edwards’ k-nearest neighbour method. Three spatio-temporal clusters of cases were detected by space–time scan analysis. The principal cluster covered 18 counties in Zhejiang during 3 to 18 April (relative risk (RR): 26.39;p<0.0001), while two secondary clusters in March and April covered 21 counties along the provincial boundary between Shanghai and Jiangsu (RR: 6.35;p<0.0001) and two counties in Jiangsu (RR: 72.48;p=0.0025). The peak of the outbreak was in the eastern coastal provinces of Zhejiang, Shanghai and Jiangsu that was characterised by statistically significant spatio-temporal aggregation, with a particularly high incidence in March and April 2013.
Highlights
A novel avian influenza A(H7N9) virus emerged in China in February 2013, causing an outbreak of human infections characterised by rapidly progressive severe illness and fatal outcome [1,2]
The case definition was based on The diagnosis and treatment programs of human infection with influenza A(H7N9) virus[18] issued by National Health and Family Planning Commission of the People’s Republic of China, in which a confirmed case of human infection with influenza A(H7N9) virus is defined as a patient with influenza-like illness, or a suspected case with respiratory specimens, testing positive for the influenza A(H7N9) virus by one of the following laboratory diagnostic tests: isolation of influenza A(H7N9) virus or real-time reverse transcription polymerase chain reaction assay for influenza A(H7N9) virus
The outbreak of human infection with influenza A(H7N9) virus has attracted considerable attention because it is an emerging infectious disease caused by a novel, reassortant avian-origin influenza virus [26,27]
Summary
A novel avian influenza A(H7N9) virus emerged in China in February 2013, causing an outbreak of human infections characterised by rapidly progressive severe illness and fatal outcome [1,2]. Strong efforts to date have been made to understand this new virus and substantial progress in epidemiology, diagnosis, therapy and aetiology of the infection has been achieved [1,7,8,9,10,11,12]. Much remains to be discovered [13], with regard to the spatial and temporal pattern of this emerging infectious disease. Understanding such patterns is essential for effective surveillance and control. A sound description of the dynamic progress of the outbreak is needed to refine control strategies and optimise resource allocation
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