Abstract
BackgroundA large number (n = 460) of A(H7N9) human infections have been reported in China from March 2013 through December 2014, and H7N9 outbreaks in humans became an emerging issue for China health, which have caused numerous disease outbreaks in domestic poultry and wild bird populations, and threatened human health severely. The aims of this study were to investigate the directional trend of the epidemic and to identify the significant presence of spatial-temporal clustering of influenza A(H7N9) human cases between March 2013 and December 2014.MethodsThree distinct epidemic phases of A(H7N9) human infections were identified in this study. In each phase, standard deviational ellipse analysis was conducted to examine the directional trend of disease spreading, and retrospective space-time permutation scan statistic was then used to identify the spatio-temporal cluster patterns of H7N9 outbreaks in humans.ResultsThe ever-changing location and the increasing size of the three identified standard deviational ellipses showed that the epidemic moved from east to southeast coast, and hence to some central regions, with a future epidemiological trend of continue dispersing to more central regions of China, and a few new human cases might also appear in parts of the western China. Furthermore, A(H7N9) human infections were clustering in space and time in the first two phases with five significant spatio-temporal clusters (p < 0.05), but there was no significant cluster identified in phase III.ConclusionsThere was a new epidemiologic pattern that the decrease in significant spatio-temporal cluster of A(H7N9) human infections was accompanied with an obvious spatial expansion of the outbreaks during the study period, and identification of the spatio-temporal patterns of the epidemic can provide valuable insights for better understanding the spreading dynamics of the disease in China.
Highlights
A large number (n = 460) of A(H7N9) human infections have been reported in China from March 2013 through December 2014, and H7N9 outbreaks in humans became an emerging issue for China health, which have caused numerous disease outbreaks in domestic poultry and wild bird populations, and threatened human health severely
Data management In order to fully examine the spread of the H7N9 outbreaks in humans, the disease data consisted of 460 influenza A(H7N9) human cases reported in China from March 2013 through December 2014, which were aggregated at the municipal level, and the spatio-temporal attributes of each H7N9 human case were used, including the location and the date of influenza A(H7N9) human cases
The results show that the largest number of influenza A(H7N9) human cases was reported from Zhejiang (142), followed by Guangdong (104), Jiangsu (62) and Shanghai (42), all of them were located in the southeast coast of China, which accounted for about 76.1% of influenza A(H7N9) human cases (350/460)
Summary
A large number (n = 460) of A(H7N9) human infections have been reported in China from March 2013 through December 2014, and H7N9 outbreaks in humans became an emerging issue for China health, which have caused numerous disease outbreaks in domestic poultry and wild bird populations, and threatened human health severely. The aims of this study were to investigate the directional trend of the epidemic and to identify the significant presence of spatial-temporal clustering of influenza A(H7N9) human cases between March 2013 and December 2014. Since the first avian influenza A (H7N9) outbreak in human occurred in March 2013 in Zhejiang, H7N9 outbreaks became an emerging issue for China health: they have caused numerous disease outbreaks in domestic poultry and wild bird populations, and threatened human health severely [1,2,3]. Understanding how A(H7N9) human infections spread in China can help controlling the epidemic in the future
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