To the Editor—As of 11 August 2013, 135 confirmed human cases of avian influenza A virus (AIV) H7N9 infection with 45 deaths were reported to the World Health Organization [1]. Recently, however, 5 reemerged cases of H7N9 infection were found in Zhejiang province, Guangdong province, and Hong Kong in China as the Northern hemisphere autumn approaches. Because most AIV-infected human cases have reported contact with poultry or live poultry markets (LPMs), we carried out surveillance for AIV in 144 LPMs in Guangzhou immediately after the first 3 confirmed human H7N9 cases were reported on 31 March 2013. From 1 April to 30 June, we sampled a total of 4598 environmental and animal swab specimens in 137 retail LPMs and 7 wholesale LPMs for the detection of AIV by reverse transcription polymerase chain reaction using 1 pair of AIV common primers and 3 pairs of primers specific to H5, H7, and H9, respectively, as described previously [2]. AIV was continually detected in both environmental and animal samples with a positive rate of 4.22% (194/4598), whereas H9 and H5 subtypes were identified for 1.65% (76/4598) and 0.54% (25/4598), respectively (Table 1). However, H7 virus was not found from these samples. The AIV-positive rate in the retail LPMs was 4.56% (177/3884), which was significantly higher than that in the wholesale LPMs (2.38% 17/714; χ2 = 7.07, P < .01), suggesting that the retail LPMs were favorable microenvironment for AIV transmission between poultry [3]. Results of Avian Influenza A Virus Surveillance in Live Poultry Markets in Guangzhou, 1 April–30 June 2013 Boldfaced values mean no significant difference (P < .05). Abbreviations: AIV, avian influenza A virus; LPM, live poultry market. a Cage, feces, chopping block, cutter, sewage. Results of Avian Influenza A Virus Surveillance in Live Poultry Markets in Guangzhou, 1 April–30 June 2013 Boldfaced values mean no significant difference (P < .05). Abbreviations: AIV, avian influenza A virus; LPM, live poultry market. a Cage, feces, chopping block, cutter, sewage. On 3 May 2013, the Guangzhou government issued a new guideline for enhanced disinfection of LPMs, including daily cleaning and weekly 1-day closure of the markets for complete disinfection. The positive rate of AIV decreased significantly from 6.95% (before the enhanced measures) to 5.97% (first month after the enhanced measures) and 1.74% (second months after the enhanced measures), respectively (trend χ2 = 14.01, P < .01). Notable, the positive rate of H9 reduced significantly from 3.48% to 2.88% and 0% during this period (trend χ2 = 12.92, P < .01). However, positive rates of AIV in animal specimens maintained at similar levels. These results indicated that enhanced disinfection measures may reduce the risk of environment-to-human transmission of AIV in LPMs. As AIV contaminated environment of conventional LPMs in China may be a high-risk location for the transmission of AIV among poultry and humans [4], permanent closure of LPMs may be a good strategy to control human AIV infections [5]. However, in a telephone survey that recruited 1196 respondents during this period, only 21.1% (95% confidence interval, 18.1%–24.4%) of respondents agreed with closing of LPMs in Guangzhou. Therefore, enhanced disinfection and regular closure of LPMs may be an alternative measure to decrease the infection risk in the conventional live poultry food supply region. Potential conflicts of interest. All authors: No reported conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.
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Yuan et al. (2013) studied this question.