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Ahead of Print -Circulation of Reassortant Influenza A(H7N9) Viruses in Poultry and Humans, Guangdong Province, China, 2013 - Volume 20, Number 12—December 2014 - Emerging Infectious Disease journal - CDC

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Ahead of Print -Circulation of Reassortant Influenza A(H7N9) Viruses in Poultry and Humans, Guangdong Province, China, 2013 - Volume 20, Number 12—December 2014 - Emerging Infectious Disease journal - CDC

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World Pneumonia Day

Volume 20, Number 12—December 2014


Circulation of Reassortant Influenza A(H7N9) Viruses in Poultry and Humans, Guangdong Province, China, 2013

Changwen Ke, Jing Lu, Jie Wu, Dawei Guan, Lirong Zou, Tie Song, Lina Yi, Xianqiao Zeng, Lijun Liang, Hanzhong Ni, Min Kang, Xin Zhang, Haojie Zhong, Jianfeng He, Jinyan Lin, Derek Smith, David Burke, Ron A.M. Fouchier, Marion Koopmans, and Yonghui ZhangComments to Author 
Author affiliations: Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China (C. Ke, J. Lu, J. Wu, D. Guan, L. Zou, T. Song, L. Yi, X. Zeng, L. Liang, H. Ni, M. Kang, X. Zhang, H. Zhong, J. He, J. Lin, Y. Zhang)University of Cambridge, Cambridge, UK (D. Smith, D. Burke)Erasmus MC, Rotterdam, the Netherlands (R.A.M. Fouchier, M. Koopmans)National Institute of Public Health and the Environment, Bilthoven, the Netherlands (M. Koopmans)


Influenza A(H7N9) virus emerged in eastern China in February 2013 and continues to circulate in this region, but its ecology is poorly understood. In April 2013, the Guangdong Provincial Center for Disease Control and Prevention (CDC) implemented environmental and human syndromic surveillance for the virus. Environmental samples from poultry markets in 21 city CDCs (n = 8,942) and respiratory samples from persons with influenza-like illness or pneumonia (n = 32,342) were tested; viruses isolated from 6 environmental samples and 16 patients were sequenced. Sequence analysis showed co-circulation of 4 influenza A(H7N9) virus strains that evolved by reassortment with avian influenza A(H9N2) viruses circulating in this region. In addition, an increase in human cases starting in late 2013 coincided with an increase in influenza A H7 virus isolates detected by environmental surveillance. Co-circulation of multiple avian influenza viruses that can infect humans highlights the need for increased surveillance of poultry and potential environmental sources.
Human infection with a novel avian-origin influenza A(H7N9) virus was first identified in eastern China in February 2013, and a major outbreak occurred from the end of March through the beginning of May (1,2). Risk factors identified for a severe course of illness were older age (>65 years) and underlying illnesses, including hypertension and chronic lung diseases, but the full spectrum of illness associated with H7N9 virus remains to be determined (3). Molecular characterization has shown that the H7N9 virus emerged by reassortment between H7, N9, and H9N2 avian influenza viruses from the Yangzi River Delta region; this reassortment likely occurred in eastern China in early 2012 (2,4,5). Because infection with H7N9 virus does not cause overt disease in poultry, the spread of infection can be insidious, and the exact modes and extent of geographic spread of the virus remain unknown. Birds commonly used for egg and meat production in China differ in their susceptibility, levels of virus shedding, and ability to transmit the virus; data from experimental infections indicate that quail and chickens are possible candidates for virus transmission (6). Detailed analysis of viruses from human patients showed evidence for diversification through reassortment of the originally detected viruses with strains from poultry in the same geographic region (7). Infection of humans is linked to exposure to poultry or to environments where poultry are present; closure of live poultry markets (LPMs) has had a measurable effect on controlling the spread of infection (8,9).
After H7N9 virus was initially detected in eastern China, the Guangdong Provincial Center for Disease Control and Prevention (CDC) implemented environmental surveillance and syndromic surveillance in humans. After H7N9 virus infection in humans was reported, enhanced sentinel hospital surveillance and environmental sampling programs were implemented to identify possible cases and analyze the evolution of the virus. The first case of human infection with H7N9 virus in Guangdong was confirmed in a patient with severe pneumonia on August 10, 2013. This case-patient was a 51-year-old female poultry worker at a local LPM in Huizhou city in Guangdong Province. No other cases were reported until October 2013, when a wave of cases began in several provinces, including Guangdong. We present results of ongoing environmental and human syndromic surveillance for H7N9 virus circulation in Guangdong Province, as well as virologic analyses related to the natural history of this outbreak.

Dr Ke is a senior scientist at Guangdong Provincial CDC, Guangdong, China, and is involved in the diagnosis and molecular epidemiology research of zoonoses and emerging infectious diseases.


This work was supported by 12th five-year-major projects of China’s Ministry of Public Health (grant no. 2012zx10004-213); the PREDICT Surveillance Animal Human Interface Project (grant no. Gvf: 06-09-057-02, to G.V.F.); and by the CASTELLUM grant, Dutch Ministry of Economic Affairs, Agriculture and Innovation (to M.K.).


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Technical Appendix

Suggested citation for this article: Ke C, Lu J, Wu J, Guan D, Zou L, Song T, et al. Circulation of reassortant influenza A(H7N9) viruses in poultry and humans, Guangdong Province, China, 2013. Emerg Infect Dis [Internet]. 2014 Dec [date cited]. http://dx.doi.org/10.3201/eid2012.140765
DOI: 10.3201/eid2012.140765

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