Abstract
The influenza A (H7N9) subtype remains a public health problem in China affecting individuals in contact with live poultry, particularly at live bird markets. Despite enhanced surveillance and biosecurity at LBMs H7N9 viruses are now more widespread in China. This study aims to quantify the temporal relationship between poultry surveillance results and the onset of human H7N9 infections during 2013–2017 and to estimate risk factors associated with geographical risk of H7N9 human infections in counties in Southeast China. Our results suggest that poultry surveillance data can potentially be used as early warning indicators for human H7N9 notifications. Furthermore, we found that human H7N9 incidence at county-level was significantly associated with the presence of wholesale LBMs, the density of retail LBMs, the presence of poultry virological positives, poultry movements from high-risk areas, as well as chicken population density and human population density. The results of this study can influence the current AI H7N9 control program by supporting the integration of poultry surveillance data with human H7N9 notifications as an early warning of the timing and areas at risk for human infection. The findings also highlight areas in China where monitoring of poultry movement and poultry infections could be prioritized.
Highlights
Since the emergence in early 2013 of a low pathogenic avian influenza (LPAI) H7N9 virus[1], there have been six epidemic waves causing about 1,600 human infections in 29 provinces and municipalities in mainland China[2]
A total of 1,181 counties from 14 provinces and municipalities in southeast China were included in this study (Fig. 1); about 93% (1408 out of 1514) of reported human H7N9 infections and 89.5% (290 out of 324) of reported H7N9 virological positive samples fell in these counties
Using the most complete data on human H7N9 infections and poultry Live bird markets (LBMs) surveillance from 2013–2017, our spatial analyses mapped the spatial distribution of human H7N9 infections and its relationship with poultry serological and virological surveillance results
Summary
Since the emergence in early 2013 of a low pathogenic avian influenza (LPAI) H7N9 virus[1], there have been six epidemic waves causing about 1,600 human infections in 29 provinces and municipalities in mainland China[2]. Recognizing the role of LBMs in the exposure and dissemination of H7N9 viruses, in Feb 2017, the Ministry of Agriculture and Rural Affairs (MARA) of China established the “1110 policy”, which includes mandatory daily market cleaning activities, disinfection, market closure once a month, and no overnight market poultry storage This policy was followed in July 2017, by the implementation of the National Vaccination Program in the poultry sector through the adoption of a bivalent H5/H7 inactivated vaccine. Other studies evaluated the role of pig density, distance to freeway, distance to national highway, landcover, temperature and relative humidity, etc.[22,25] None of these studies looked at the effect of more proximal factors such as poultry surveillance results and live chicken movement in explaining the geographical variation of human H7N9 infections
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