Abstract
BackgroundPrevious studies have proven that the closure of live poultry markets (LPMs) was an effective intervention to reduce human risk of avian influenza A (H7N9) infection, but evidence is limited on the impact of scale and duration of LPMs closure on the transmission of H7N9.MethodFive cities (i.e., Shanghai, Suzhou, Shenzhen, Guangzhou and Hangzhou) with the largest number of H7N9 cases in mainland China from 2013 to 2017 were selected in this study. Data on laboratory-confirmed H7N9 human cases in those five cities were obtained from the Chinese National Influenza Centre. The detailed information of LPMs closure (i.e., area and duration) was obtained from the Ministry of Agriculture. We used a generalized linear model with a Poisson link to estimate the effect of LPMs closure, reported as relative risk reduction (RRR). We used classification and regression trees (CARTs) model to select and quantify the dominant factor of H7N9 infection.ResultsAll five cities implemented the LPMs closure, and the risk of H7N9 infection decreased significantly after LPMs closure with RRR ranging from 0.80 to 0.93. Respectively, a long-term LPMs closure for 10–13 weeks elicited a sustained and highly significant risk reduction of H7N9 infection (RRR = 0.98). Short-time LPMs closure with 2 weeks in every epidemic did not reduce the risk of H7N9 infection (p > 0.05). Partially closed LPMs in some suburbs contributed only 35% for reduction rate (RRR = 0.35). Shenzhen implemented partial closure for first 3 epidemics (p > 0.05) and all closure in the latest 2 epidemic waves (RRR = 0.64).ConclusionOur findings suggest that LPMs all closure in whole city can be a highly effective measure comparing with partial closure (i.e. only urban closure, suburb and rural remain open). Extend the duration of closure and consider permanently closing the LPMs will help improve the control effect. The effect of LPMs closure seems greater than that of meteorology on H7N9 transmission.
Highlights
Previous studies have proven that the closure of live poultry markets (LPMs) was an effective intervention to reduce human risk of avian influenza A (H7N9) infection, but evidence is limited on the impact of scale and duration of LPMs closure on the transmission of H7N9
Short-time LPMs closure with 2 weeks in every epidemic did not reduce the risk of H7N9 infection (p > 0.05)
Three cities are around the Yangtze River Delta: 1) In Shanghai, all LPMs were closed from the beginning of the Spring Festive to the end of April in each wave; 2) In Suzhou, closed all the LPMs in the first 3 waves, since the closure measure only was implemented in urban area of city; 3) In Hangzhou, LPMs closure implemented partially in urban area during five waves
Summary
Previous studies have proven that the closure of live poultry markets (LPMs) was an effective intervention to reduce human risk of avian influenza A (H7N9) infection, but evidence is limited on the impact of scale and duration of LPMs closure on the transmission of H7N9. Since the first laboratory-confirmed human infection with avian influenza A (H7N9) was reported on 31 March 2013, epidemics of human infections of H7N9 virus in mainland China have generally followed a seasonal trend, with five previous major outbreaks on record [1]. One of the main ways people are exposed to the H7N9 virus is through exposure to live poultry markets (LPMs). A prior study suggested that the retail but not the wholesale LPMs are strongly associated with human H7N9 infection risk [6, 7]. 48% of respondents reported that they raised backyard poultry [9], while for cities the highest influenza A positive rates were detected at the retail LPMs [6]
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