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H7N9 Spreading Westward from Southern and Eastern China

JUN 04, 2018 | NICOLA M. PARRY, BVSC, MRCVS, MSC, DACVP, ELS
A recent study has shown that highly pathogenic avian influenza (HPAI) A(H7N9) virus is spreading westward from southern and eastern China.

Qiqi Yang, Wei Shi, and Lei Zhang, from Beijing Normal University, China, and colleagues published the results of their study online in the June 2018 issue of Emerging Infectious Diseases, the Centers for Disease Control and Prevention’s (CDC) monthly peer-reviewed public health journal. 

“We report cases of human infection with H7N9 virus, including in 1 person who was infected with a highly pathogenic variant, in Shaanxi Province, western China, during April and May 2017,” the authors write.

Since it emerged in 2013, the H7N9 virus has triggered five epidemics of infections in individuals in China. These waves have taken a heavy toll on human health, resulting in 1,564 laboratory-confirmed cases and 612 deaths.

According to the authors, the first four waves of infections were limited to eastern and southern China. However, the fifth spread north, and also infected many more individuals. Since then, additional cases of H7N9 have also been reported in southern China.

In their study, Yang, Shi, Zhang and colleagues analyzed samples from 5 patients from Shaanxi Province in western China with confirmed H7N9 infections. One patient was infected with HPAI H7N9, and the other 4 were infected with low pathogenicity avian influenza (LPAI) A(H7N9). Two of the patients infected with LPAI died.

The researchers analyzed respiratory tract specimens from all of these patients, in the form of either throat swabs or sputum samples. And, because human cases of H7N9 have been mostly traced to exposure to the virus at live poultry markets (LPMs) in mainland China, the researchers also examined 496 samples from LPMs and poultry farms from 4 cities in Shaanxi Province. These specimens included samples of poultry feces and swabs from poultry cages.

Of the LPM specimens, 14 tested positive for H7N9, the authors say.

By using genome sequencing techniques, they also found that the viruses from these LPM specimens and the sample from the patient with HPAI were similar and were all confirmed as HPAI.

When the researchers analyzed the HPAI viruses, they found similarities between them and previously isolated HPAI viruses from cases in southern China. The LPAI H7N9 viruses isolated from patients in Shaanxi Province were also similar to LPAI viruses previously identified in regions of eastern, central, and southern China. These findings highlight spread of both LPAI and HPAI H7N9 into western China.

Genetic analysis of H7N9 virus from infected humans in two cities in Shaanxi Province also showed genetic similarities with H7N9 from LPMs and poultry farms in the same regions.

Consistent with previous studies highlighting that poultry trade may be spreading H7N9 viruses, these results of this current study “provide evidence that H7N9 viruses infecting humans in Shaanxi Province derived, directly or indirectly, from strains circulating in local farms and LPMs,” the authors conclude.
 
Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.
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