H7N9 influenza virus surveillance in Gansu, China in 2017.

• Avian influenza A(H7N9) virus caused serious disease and threaten to public health. • Five human cases were investigated during the surveillance in 2017, Gansu, China. • Positive A(H7N9) environmental samples were detected in the same location and period. • At least two routers, via which A(H7N9) viruses were introduced to Gansu, in 2017. Avian H7N9 influenza virus, which emerged in 2013 China, had caused the fifth wave of peaks in 2016–2017. Gansu Province locate in western China far away from the epicenter of the virus, also detected cases in this wave. During the monitoring, five human cases with H7N9 virus infection, three cases in Jiuquan and two cases in Zhangye, were reported and investigated. A total of 88 environmental samples collected from March to June, in poultry farms and live poultry markets were H7N9 positive by real time RT-PCR assay. The two human viruses were identified as LPAI viruses, and phylogenetic analysis showed that the viruses might be introduced into Gansu by two distinct trade routes. Avian influenza H7N9virus posed a pandemic potential to threaten human health, and monitoring among birds and the environment should be strengthened. [ABSTRACT FROM AUTHOR]