DOI:10.1111/irv.12288 www.influenzajournal.com
Letter to the Editor
Antibodies against influenza A (H7N9) virus among veterinarians in China before 2013 Xiuchen Yin,a Jie Tao,a Fanglong Zhao,a Baizhong Rao,a Huili Liua,b a Institute of Animal Science and Veterinary Medicine, Shanghai Academy of Agricultural Sciences, Shanghai, China. bShanghai Municipal Key Laboratory of Agri-genetics and Breedings, Shanghai, China. Correspondence: Huili Liu, Institute of Animal Science and Veterinary Medicine, Shanghai Academy of Agricultural Sciences, Shanghai, China. E-mail: [email protected]
Accepted 17 August 2014. Published Online 29 October 2014.
Please cite this paper as: Yin et al. (2015) Antibodies against influenza A (H7N9) virus among veterinarians in China before 2013. Influenza and Other Respiratory Viruses 9(1), 38–39.
To the editor: A recent outbreak of a novel avian-origin reassortant influenza A (H7N9) virus in eastern China has raised great concerns owing to the rapidly progressive lower respiratory tract infections in infected individuals. As of August 1, 2014, a total of 151 humans infections of H7N9 (resulting in 45 deaths) in China have been reported to the World Health Organization.1 Indeed, inclusion of a wide range of high-risk groups often provides a better understanding of immunogenic responses to a novel influenza virus infection. A previous serologic study (conducted by Yuelong Shu and colleagues) did not find any evidence for human infection with the novel avian-origin influenza A (H7N9) virus in poultry workers before 2013 in southeastern China.2 The other serologic study conducted in Zhejiang province found that 741 healthcare and non-healthcare workers did not have subclinical or asymptomatic A (H7N9) infection and suggested that more extensive serological investigation of asymptomatic or subclinical A (H7N9) infection among different high-risk groups in various regions should be performed in China.3 Of critical importance in this regard is the fact that occupational groups studied have not included veterinarians. Epidemiological and serological evidence have already indicated that poultry farm and live market workers are high-risk groups.2,4 However, due to the nature of their work environment and practices, veterinarians are also at high risk of exposure to avian influenza virus and may have more intense and frequent exposure to diseased poultry than poultry workers themselves.4,5 To assess whether subclinical human infection with the novel H7N9 virus occurred in the other poultry exposure group (veterinarians) before 2013, we collected single serum samples anonymously from practicing veterinarians
38
(n = 820: 288 from Shanghai, 192 from Anhui, 199 from Zhejiang, and 141 from Gangsu) during December 2011 to December 2012 (Table 1). We employed a hemagglutination inhibition (HI) assay according to the WHO instructions.6 Our HI assay used horse erythrocytes instead of chicken red blood cells (RBCs), to increase the assay sensitivity. An H7 antigen A/pigeon/Shanghai/S1421/2013(H7N9) derived from the emergent H7N9 AIV was obtained from the Chinese Academy of Agricultural Sciences (CAAS), Harbin Veterinary Research Institute (Harbin, China). A serum sample was considered positive when the HI titer ≥80.3 Sera from the veterinarians were also studied for antibodies against influenza A (H7N9) virus using a new competitive ELISA kit that targets H7 hemagglutinin antigen (Immune Technology, Suzhou, China).7 Negative control serum and positive control serum specimens were included in each plate to provide a diverse range of controls. None of the samples were positive for H7 AIV infection by HA-specific ELISA and HI assays using ≥80 cut-off antibody Table 1. Characteristics of participants in the serological survey in China before 2013
No. demographic description
Locations
No.
Median of age (range)
Shanghai Anhui Zhejiang Gansu
288 192 199 141
37 43 34 41
(23–63) (29–66) (24–53) (21–60)
No. of female (%)
Median of occupation age at time of poultry contact
31 20 15 12
1733 2037 1356 1448
(1076) (1042) (758) (851)
ª 2014 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Letter to the Editor
titer. Although HI titers of 20 were detected in 19 of 820 serum samples, the lower 40 titers might have resulted from cross-reactivity with previous human influenza virus infections. None of the veterinarians had evidence of previous infection with the emergent H7N9 AIV before 2013. Our serologic study first found no evidence for human infection with the novel avian-origin influenza A (H7N9) virus in veterinarians before 2013 in China. To our knowledge, this is the first investigation of seroprevalence of Influenza A (H7N9) in occupationally exposed veterinarians in eastern China. A better understanding of interspecies transmission of avian influenza is a crucial component in efforts to minimize the effects of the next pandemic. First, high-risk groups with frequent and close contact to infected avians may be among the first to be infected and, by spreading the illness to their families and communities, may serve as a bridging population to the general population. Second, different to the other high-risk groups, the veterinary with frequent and close contact to other infected animals. As none-avian animals such as pigs and dogs in China have been shown to be infected with AIVs,7–9 seasonal influenza vaccination is recommended for veterinary, to reduce the risk of joint infections with human and avian viruses and consequent risk of virus reassortment or recombination. As novel viruses may rapidly change, it seems prudent to continue surveillance for the H7N9 virus among high-risk groups such as poultry workers, veterinarians, healthcare and non-healthcare workers.
Acknowledgements The research was supported by Shanghai Agricultural Commission Talented Project for Youth: No. 2012-QJ09; No. 2014-1-35.
Ethical approval This study protocol was reviewed and approved by the Institutional Review Board at the Jiangsu Center for Disease Control and Prevention.
References 1 World Health Organization (WHO). Available at: http://www.who. int/influenza/human_animal_interface/influenza_h7n9/en/index.html? treeid=BEAC9C103DF952C4&nowtreeid=9A24F7E6CF505AA3 (Accessed 10 May 2013). 2 Bai T, Zhou J, Shu Y. Serologic study for influenza A (H7N9) among high-risk groups in China. N Engl J Med 2013; 368:2339–2340. 3 Xu W, Lu L, Shen B. Serological investigation of subclinical influenza A (H7H9) infection among healthcare and non-healthcare workers in Zhejiang Province of China. Clin Infect Dis 2013; 57:919–921. 4 Koopmans M, Wilbrink B, Conyn M, Natrop G, van der Nat H, Vennema H. Transmission of H7N7 avian influenza A virus to human beings during a large outbreak in commercial poultry farms in the Netherlands. Lancet 2004; 363:587–593. 5 Myers KP, Setterquist SF, Capuano AW. Infection due to 3 avian influenza subtypes in United States veterinarians. Clin Infect Dis 2007; 45:4–9. 6 World Health Organization. 2011. Manual for the laboratory diagnosis and virological surveillance of influenza. Available at: http://www.who. int/influenza/gisrs_laboratory/manual_diagnosis_surveillance_influenza/ en/ (Accessed 8–10 March 2011). 7 Su S, Zhou P, Fu X et al. Virological and epidemiological evidence of avian influenza virus infections among feral dogs in live poultry markets, China. A threat to human health? Clin Infect Dis 2014; 58:1644–1646. 8 Su S, Qi W, Zhou P et al. First evidence of H10N8 avian influenza virus infections among feral dogs in live poultry markets in Guangdong Province, China. Clin Infect Dis 2014; 59:748–750. 9 Su S, Gregory GC, Lu JH, Liao M, Zhang GH, Li SJ. New “One Health” strategies needed for emerging pathogens detection and control at Cantonese live animal markets, China. Clin Infect Dis 2014; 59:1194– 1197.
Competing interests None declared.
ª 2014 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd.
39
Copyright of Influenza & Other Respiratory Viruses is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Letter to the Editor
Antibodies against influenza A (H7N9) virus among veterinarians in China before 2013 Xiuchen Yin,a Jie Tao,a Fanglong Zhao,a Baizhong Rao,a Huili Liua,b a Institute of Animal Science and Veterinary Medicine, Shanghai Academy of Agricultural Sciences, Shanghai, China. bShanghai Municipal Key Laboratory of Agri-genetics and Breedings, Shanghai, China. Correspondence: Huili Liu, Institute of Animal Science and Veterinary Medicine, Shanghai Academy of Agricultural Sciences, Shanghai, China. E-mail: [email protected]
Accepted 17 August 2014. Published Online 29 October 2014.
Please cite this paper as: Yin et al. (2015) Antibodies against influenza A (H7N9) virus among veterinarians in China before 2013. Influenza and Other Respiratory Viruses 9(1), 38–39.
To the editor: A recent outbreak of a novel avian-origin reassortant influenza A (H7N9) virus in eastern China has raised great concerns owing to the rapidly progressive lower respiratory tract infections in infected individuals. As of August 1, 2014, a total of 151 humans infections of H7N9 (resulting in 45 deaths) in China have been reported to the World Health Organization.1 Indeed, inclusion of a wide range of high-risk groups often provides a better understanding of immunogenic responses to a novel influenza virus infection. A previous serologic study (conducted by Yuelong Shu and colleagues) did not find any evidence for human infection with the novel avian-origin influenza A (H7N9) virus in poultry workers before 2013 in southeastern China.2 The other serologic study conducted in Zhejiang province found that 741 healthcare and non-healthcare workers did not have subclinical or asymptomatic A (H7N9) infection and suggested that more extensive serological investigation of asymptomatic or subclinical A (H7N9) infection among different high-risk groups in various regions should be performed in China.3 Of critical importance in this regard is the fact that occupational groups studied have not included veterinarians. Epidemiological and serological evidence have already indicated that poultry farm and live market workers are high-risk groups.2,4 However, due to the nature of their work environment and practices, veterinarians are also at high risk of exposure to avian influenza virus and may have more intense and frequent exposure to diseased poultry than poultry workers themselves.4,5 To assess whether subclinical human infection with the novel H7N9 virus occurred in the other poultry exposure group (veterinarians) before 2013, we collected single serum samples anonymously from practicing veterinarians
38
(n = 820: 288 from Shanghai, 192 from Anhui, 199 from Zhejiang, and 141 from Gangsu) during December 2011 to December 2012 (Table 1). We employed a hemagglutination inhibition (HI) assay according to the WHO instructions.6 Our HI assay used horse erythrocytes instead of chicken red blood cells (RBCs), to increase the assay sensitivity. An H7 antigen A/pigeon/Shanghai/S1421/2013(H7N9) derived from the emergent H7N9 AIV was obtained from the Chinese Academy of Agricultural Sciences (CAAS), Harbin Veterinary Research Institute (Harbin, China). A serum sample was considered positive when the HI titer ≥80.3 Sera from the veterinarians were also studied for antibodies against influenza A (H7N9) virus using a new competitive ELISA kit that targets H7 hemagglutinin antigen (Immune Technology, Suzhou, China).7 Negative control serum and positive control serum specimens were included in each plate to provide a diverse range of controls. None of the samples were positive for H7 AIV infection by HA-specific ELISA and HI assays using ≥80 cut-off antibody Table 1. Characteristics of participants in the serological survey in China before 2013
No. demographic description
Locations
No.
Median of age (range)
Shanghai Anhui Zhejiang Gansu
288 192 199 141
37 43 34 41
(23–63) (29–66) (24–53) (21–60)
No. of female (%)
Median of occupation age at time of poultry contact
31 20 15 12
1733 2037 1356 1448
(1076) (1042) (758) (851)
ª 2014 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Letter to the Editor
titer. Although HI titers of 20 were detected in 19 of 820 serum samples, the lower 40 titers might have resulted from cross-reactivity with previous human influenza virus infections. None of the veterinarians had evidence of previous infection with the emergent H7N9 AIV before 2013. Our serologic study first found no evidence for human infection with the novel avian-origin influenza A (H7N9) virus in veterinarians before 2013 in China. To our knowledge, this is the first investigation of seroprevalence of Influenza A (H7N9) in occupationally exposed veterinarians in eastern China. A better understanding of interspecies transmission of avian influenza is a crucial component in efforts to minimize the effects of the next pandemic. First, high-risk groups with frequent and close contact to infected avians may be among the first to be infected and, by spreading the illness to their families and communities, may serve as a bridging population to the general population. Second, different to the other high-risk groups, the veterinary with frequent and close contact to other infected animals. As none-avian animals such as pigs and dogs in China have been shown to be infected with AIVs,7–9 seasonal influenza vaccination is recommended for veterinary, to reduce the risk of joint infections with human and avian viruses and consequent risk of virus reassortment or recombination. As novel viruses may rapidly change, it seems prudent to continue surveillance for the H7N9 virus among high-risk groups such as poultry workers, veterinarians, healthcare and non-healthcare workers.
Acknowledgements The research was supported by Shanghai Agricultural Commission Talented Project for Youth: No. 2012-QJ09; No. 2014-1-35.
Ethical approval This study protocol was reviewed and approved by the Institutional Review Board at the Jiangsu Center for Disease Control and Prevention.
References 1 World Health Organization (WHO). Available at: http://www.who. int/influenza/human_animal_interface/influenza_h7n9/en/index.html? treeid=BEAC9C103DF952C4&nowtreeid=9A24F7E6CF505AA3 (Accessed 10 May 2013). 2 Bai T, Zhou J, Shu Y. Serologic study for influenza A (H7N9) among high-risk groups in China. N Engl J Med 2013; 368:2339–2340. 3 Xu W, Lu L, Shen B. Serological investigation of subclinical influenza A (H7H9) infection among healthcare and non-healthcare workers in Zhejiang Province of China. Clin Infect Dis 2013; 57:919–921. 4 Koopmans M, Wilbrink B, Conyn M, Natrop G, van der Nat H, Vennema H. Transmission of H7N7 avian influenza A virus to human beings during a large outbreak in commercial poultry farms in the Netherlands. Lancet 2004; 363:587–593. 5 Myers KP, Setterquist SF, Capuano AW. Infection due to 3 avian influenza subtypes in United States veterinarians. Clin Infect Dis 2007; 45:4–9. 6 World Health Organization. 2011. Manual for the laboratory diagnosis and virological surveillance of influenza. Available at: http://www.who. int/influenza/gisrs_laboratory/manual_diagnosis_surveillance_influenza/ en/ (Accessed 8–10 March 2011). 7 Su S, Zhou P, Fu X et al. Virological and epidemiological evidence of avian influenza virus infections among feral dogs in live poultry markets, China. A threat to human health? Clin Infect Dis 2014; 58:1644–1646. 8 Su S, Qi W, Zhou P et al. First evidence of H10N8 avian influenza virus infections among feral dogs in live poultry markets in Guangdong Province, China. Clin Infect Dis 2014; 59:748–750. 9 Su S, Gregory GC, Lu JH, Liao M, Zhang GH, Li SJ. New “One Health” strategies needed for emerging pathogens detection and control at Cantonese live animal markets, China. Clin Infect Dis 2014; 59:1194– 1197.
Competing interests None declared.
ª 2014 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd.
39
Copyright of Influenza & Other Respiratory Viruses is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
