Abstract
After a series of studies on the pathogenicity of several H7N9 strains from 2013 to 2018, we wanted to dynamically track the pathogenicity of A/Guangdong/Th005/2017 in ferrets and poultry. The pathogenicity and transmissibility of Th005, especially the distribution and replication in tissues, were studied in ferrets. We also aimed to assess the level of Th005 pathogenicity in chickens. The results showed that the pathogenicity of Th005 was significantly increased in ferrets and chickens, especially compared with the Anhui strain. The replication of Th005 in the lung tissues of ferrets was 100-fold higher than that of the Anhui strain. Th005 pathogenicity reached an intravenous pathogenicity index (IVPI) score of 3 in avian models. Continuously high titres of viruses could be detected in the cloacal cavity of chickens infected with Th005. Th005 remained highly pathogenic in mice and chickens after passaging in ferrets. High expression of both the α2,6- and α2,3-sialic acid residues in cells in vitro was beneficial to Th005 replication, which was enhanced compared to the Anhui strain. China needs to strengthen its surveillance of virulent influenza virus strains, such as Th005, which continues to increase in pathogenicity.
Highlights
The first human infection with the influenza H7N9 strain appeared in the Yangtze River Delta region in March 2013 [1]
The first human infection with an H7N9 strain appeared in the Yangtze River Delta region in
As early as 2013, H7N9 strains isolated from patients during the first wave of infection were studied in ferrets for their pathogenicity and transmissibility, as well as the upper respiratory tract symptoms they caused, such as nasal discharge and sneezing
Summary
The first human infection with the influenza H7N9 strain appeared in the Yangtze River Delta region in March 2013 [1]. Between January 2013 and January 2019, the virus caused 1567 infections and 615 deaths. Molecular biological analyses have shown that the H7N9 influenza virus has changed from low pathogenicity to high pathogenicity [3]. The world organization for animal health (OIE) has reported numerous chicken deaths in poultry farms in China, with H7N9 avian influenza viruses isolated from chickens [4]. It is unclear how the H7N9 viruses have spread in nature and become highly pathogenic.
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