Emergence and development of H7N9 influenza viruses in China

•H7N9 virus was generated through sequential reassortments in ducks and chickens.•This virus originated from eastern China and has spread to over 20 provinces.•Regionally distinct lineages have been established with different genotypes.•Viruses present at live poultry markets fueled the recurrence o...

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Bibliographic Details
Published in:Current opinion in virology 2016-02, Vol.16, p.106-113
Main Authors: Zhu, Huachen, Lam, Tommy Tsan-Yuk, Smith, David Keith, Guan, Yi
Format: Article
Language:English
Subjects:
Animals
Chickens
China - epidemiology
Communicable Diseases, Emerging
Ducks
Evolution, Molecular
Genotype
Humans
Influenza A Virus, H7N9 Subtype - classification
Influenza A Virus, H7N9 Subtype - genetics
Influenza A Virus, H7N9 Subtype - isolation & purification
Influenza in Birds - epidemiology
Influenza in Birds - transmission
Influenza in Birds - virology
Influenza, Human - epidemiology
Influenza, Human - transmission
Influenza, Human - virology
Phylogeny
Reassortant Viruses
Risk Factors
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Summary:•H7N9 virus was generated through sequential reassortments in ducks and chickens.•This virus originated from eastern China and has spread to over 20 provinces.•Regionally distinct lineages have been established with different genotypes.•Viruses present at live poultry markets fueled the recurrence of human infections.•Chickens served as the source of human infections in each outbreak wave. The occurrence of human infections with avian H7N9 viruses since 2013 demonstrates the continuing pandemic threat posed by the current influenza ecosystem in China. Influenza surveillance and phylogenetic analyses showed that these viruses were generated by multiple interspecies transmissions and reassortments among the viruses resident in domestic ducks and the H9N2 viruses enzootic in chickens. A large population of domestic ducks hosting diverse influenza viruses provided the precondition for these events to occur, while acquiring internal genes from enzootic H9N2 influenza viruses in chickens promoted the spread of these viruses. Human infections effectively act as sentinels, reflecting the intensity of the activity of these viruses in poultry.
ISSN:1879-6257
1879-6265
DOI:10.1016/j.coviro.2016.01.020