Emergence of human avian influenza A(H7N9) virus infections in Wenshan City in Southwest China, 2017

Abstract

Background: The emergence of human infection with avian influenza A(H7N9) virus was reported in Wenshan City, southwestern China in 2017. The study describes the epidemiological and virological features of the outbreak and discusses the origin of the infection. Methods: Poultry exposure and timelines of key events for each patient were collected. Samples derived from the patients, their close contacts, and environments were tested for influenza A(H7N9) virus by real-time reverse transcription polymerase chain reaction. Genetic sequencing and phylogenetic analysis were also conducted. Results: Five patients were reported in the outbreak. An epidemiological investigation showed that all patients had been exposed at live poultry markets. The A(H7N9) isolates from these patients had low pathogenicity in avian species. Both epidemiological investigations of chicken sources and phylogenetic analysis of viral gene sequences indicated that the source of infection was from Guangxi Province, which lies 100 km to the east of Wenshan City. Conclusions: In the study, a sudden emergence of human cases of H7N9 was documented in urban area of Wenshan City. Chickens were an important carrier in the H7N9 virus spreading from Guangxi to Wenshan. Hygienic management of live poultry markets and virological screening of chickens transported across regions should be reinforced to limit the spread of H7N9 virus.

Emergence of Human Avian-Influenza

“…Whereas, pandemic influenza is only caused by influenza A viruses [4]. Influenza in humans that are caused by avian influenza viruses which are transmitted across species to humans is known as human-avian influenza [8].…”

“…The following are avian influenza viruses that have been recognized to cause human-avian influenza: H5N6, H6N1, H7N2, H7N3, H7N4, H5N8, H5N1, H5N8, H7N9, H9N2, H10N7 and H10N8 [8,[10][11][12]. Human-avian influenza which is caused by an Asian H7N9 virus was first reported in in 2013.…”

Emergence of novel avian origin H7N9 viruses after introduction of H7‐Re3 and rLN79 vaccine strains to China

“…Under a mandatory immunization policy, the prevalence of the H7N9 viruses has declined markedly within China since 2018 (Shi et al, 2017;Shi et al, 2018). However, human fatalities triggered by the H7N9 variant strains are still being recorded in some areas (Li et al, 2021), and these events demonstrate that even under vaccine protection, the H7N9 subtype HPAI viruses are still able to pose a threat to public safety (Jiang, Zhao, et al, 2020;Li et al, 2019).…”