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. 2016 May;60(1 Suppl):118-25.
doi: 10.1637/11098-042015-Reg.

Detection of Avian H7N9 Influenza A Viruses in the Yangtze Delta Region of China During Early H7N9 Outbreaks

Yin Li  1   2   3 , Xin-Mei Huang  1   2   3 , Dong-Min Zhao  1   2   3 , Yu-Zhuo Liu  1   2   3 , Kong-Wang He  1   2 , Yao-Xing Liu  4 , Chang-Hai Chen  4 , Li-Ping Long  5 , Yifei Xu  5 , Xing-Xing Xie  1   2 , Kai-Kai Han  1   2 , Xiao-Yan Liu  1   2 , Jing Yang  1   2 , You-Fa Zhang  6 , Feng Fan  7 , Richard Webby  8 , Xiu-Feng Wan  5
Affiliations

Detection of Avian H7N9 Influenza A Viruses in the Yangtze Delta Region of China During Early H7N9 Outbreaks

Yin Li et al. Avian Dis. 2016 May.

Abstract

Since the first H7N9 human case in Shanghai, February 19, 2013, the emerging avian-origin H7N9 influenza A virus has become an epizootic virus in China, posing a potential pandemic threat to public health. From April 2 to April 28, 2013, some 422 oral-pharyngeal and cloacal swabs were collected from birds and environmental surfaces at five live poultry markets (LPMs) and 13 backyard poultry farms (BPFs) across three cities, Wuxi, Suzhou, and Nanjing, in the Yangtze Delta region. In total 22 isolates were recovered, and six were subtyped as H7N9, nine as H9N2, four as H7N9/H9N2, and three unsubtyped influenza A viruses. Genomic sequences showed that the HA and NA genes of the H7N9 viruses were similar to those of the H7N9 human isolates, as well as other avian-origin H7N9 isolates in the region, but the PB1, PA, NP, and MP genes of the sequenced viruses were more diverse. Among the four H7N9/H9N2 mixed infections, three were from LPM, whereas the other one was from the ducks at one BPF, which were H7N9 negative in serologic analyses. A survey of the bird trading records of the LPMs and BPFs indicates that trading was a likely route for virus transmission across these regions. Our results suggested that better biosecurity and more effective vaccination should be implemented in backyard farms, in addition to biosecurity management in LPMs.

Keywords: H7N9; avian influenza virus; backyard poultry farm; domestic poultry; influenza A virus; live poultry market; wild bird.

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Figures

Figure 1
Figure 1
The H7N9 positive LPMs and the poultry trades associated with these LPMs. (A) Geographical distributions of reported human case during early stage of H7N9 outbreaks. The number of the human cases is indicated in the parenthesis. Abbreviations: AH, Anhui; BJ, Beijing; FJ, Fujian; GD, Guangdong; HB, Hebei; HN, Henan; HN, Hunan; JX, Jiangxi; SD, Shandong; SH, Shanghai; TW, Taiwan; ZJ, Zhejiang. (B) Poultry trade between H7N9 positive LPMs in Jiangsu and nearby provinces. Our surveillance recovered H7N9 viruses from LPM A (Suzhou, 4/2/2013), D (Wuxi, 4/5/2013), and E (Wuxi, 4/5/2013). The birds from these markets were trading with at least 8 regions from Anhui, Henan, Hebei, and Shandong. These four regions were later reported with H7N9 human cases. (C) Poultry trade between H7N9 positive LPMs and nearby cities in Jiangsu province. The disease onset dates of the H7N9 cases are notified.
Figure 2
Figure 2
An emergence and transmission model of H7N9 low pathogenic avian influenza viruses in Yangtze Delta Region. The H7N9 low pathogenic avian influenza viruses could emerge in backyard birds at BPFs through the interactions among migratory waterfowl and backyard birds. The birds from BPFs can carry H7N9 viruses into the LPMs, especially wholesale LPMs, where these viruses can quickly spread to other birds on the wholesale LPMs. The wholesale markets serve as the sources supplying these viruses into individual local LPMs. The model describes five major risk components in animal-influenza components, including LPM, transportation vectors, BPF, domestic poultry farm, and wild bird population. Among these risk components, LPMs are still primary sources for influenza exposures and infections for man.
Figure 3
Figure 3
Phylogenetic analyses of HA and NA genes of H7N9 low pathogenic avian influenza viruses. The genes from this surveillance are underlined, and bootstrap values for representative lineages are marked.
Figure 3
Figure 3
Phylogenetic analyses of HA and NA genes of H7N9 low pathogenic avian influenza viruses. The genes from this surveillance are underlined, and bootstrap values for representative lineages are marked.
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