Environmental connections of novel avian-origin H7N9 influenza virus infection and virus adaptation to the human

Abstract

A novel H7N9 influenza A virus has been discovered as the causative identity of the emerging acute respiratory infection cases in Shanghai, China. This virus has also been identified in cases of infection in the neighboring area Hangzhou City in Zhejiang Province. In this study, epidemiologic, clinical, and virological data from three patients in Hangzhou who were confirmed to be infected by the novel H7N9 influenza A virus were collected and analyzed. Human respiratory specimens and chicken feces from a contacted free market were tested for influenza virus by real-time reverse transcription PCR (RT-PCR) and sequencing. The clinical features of the three cases were similar featured with high fever and severe respiratory symptoms; however, only one of the patients died. A certain degree of diversity was observed among the three Hangzhou viruses sequenced from human samples compared with other reported H7N9 influenza A viruses. The sequences of the novel avian-origin H7N9 influenza viruses from Hangzhou City contained important amino acid substitutions related to human adaptation. One of the Hangzhou viruses had gained a novel amino acid substitution (Q226I) in the receptor binding region of hemagglutinin. More importantly, the virus sequenced from the chicken feces had a 627E substitution in the PB2 protein instead of the mammalian-adapted 627K substitution that was found in the PB2 proteins from the Hangzhou viruses from the three patients. Therefore, the newly-emerging H7N9 virus might be under adaptation pressure that will help it "jump" from avian to human hosts. The significance of these substitutions needs further exploration, with both laboratory experiments and extensive field surveillance. H7N9 influenza A virus, human adaptation, epidemiology, substitution Citation:Li J, Yu X F, Pu X Y, et al. Environmental connections of novel avian-origin H7N9 influenza virus infection and virus adaptation to the human. Sci China Life Sci, 2013, 56: 485-492,

Lessons learnt from the human infections of avian-origin influenza A H7N9 virus: Live free markets and human health

“…Agriculture sector argues that the H7N9 does not cause any diseases for poultry therefore it should not be called avian influenza virus. Whereas Li et al [4] unambiguously demonstrated the relatedness of human infection with poultry or poultry related market. The question can be open for further discussion and we also need to see the circulation trends of the virus in the future.…”

“…Unlike the highly pathogenic H5N1 virus, which kills the birds [1-3], H7N9 is avirulent to either domestic poultry or migratory birds, which makes the situation even worse as it is hard to identify the birds who carry the viruses. In this issue of SCIENCE CHINA Life Sciences, Li et al [4] present solid evidence that the human infecting H7N9 viruses are directly from the live free markets, where some patients visited before falling ill. In accordance with a report in The Lancet [5], the work also shows the avian-signature sequences from the environment where chickens are kept in the free market and human-signature sequences in the patients, implying the in-vivo micro-evolution and host adaptation during the outbreak and infection.…”

“…Later the viruses were isolated from pigeons, quails and their environments [8]. Now Li et al [4] report three H7N9-infected patients and one of them visited a live free market. Virus genome sequence from this particular patient matched well with the virus sequence derived from the swab of the chicken cage in the market, except for the chicken-versus human-signature substitutions.…”

Dynamic reassortments and genetic heterogeneity of the human-infecting influenza A (H7N9) virus

“…A single reoccurring case was just reported on 15 October, in Zhejiang Province, China. Until now, there have been no confirmed cases of human-to-human transmission, and most infected humans had a history of contact with poultry or of having visited a wet market [2][3][4][5][6] , although suspected human-to-human transmission has been described 7 . Our previous analyses on the first released virus genomes proposed that this virus might have emerged from at least four origins by means of genetic reassortment 3 .…”

Continuing Reassortment Leads to the Genetic Diversity of Influenza Virus H7N9 in Guangdong, China

“…According to the epidemiology and sequence analyses, H7N9 virus-contaminated live-poultry markets (LPM) are regarded as the major sources of the human infections with the H7N9 virus (6)(7)(8). Therefore, after the initial report of H7N9 influenza virus infection in humans in March 2013, environmental sampling programs and enhanced sentinel hospital surveillance were implemented in Guangdong in order to identify possible cases of infection and to analyze the evolution of the virus.…”