On September 25, 2022, highly pathogenic avian influenza virus (HPAIV) was detected in a peregrine falcon that died after weakening in Isehara City, Kanagawa Prefecture. The National Agriculture and Food Research Organization (NARO) has conducted whole-genome sequencing of this virus. From this analysis, it was revealed that this virus is closely related to the H5N1 HPAIV that caused outbreaks in Japan in the 2021/2022 season (autumn 2021 to spring 2022). HPAIV infection cases were confirmed in wild birds in Japan at the earliest time of the season since 2004, and HPAI outbreaks were also reported in domestic poultry in late October this year. Therefore, an increased alert is required to prevent the introduction of virus to poultry farms.
In the surveillance of highly pathogenic avian influenza (HPAI) in wild birds conducted by the Ministry of the Environment and prefectures in Japan, a weakened peregrine falcon was collected in Isehara City, Kanagawa Prefecture on 25 September 2022, and died the following day. After the confirmation of the influenza A virus by the commercial rapid test, genetic analysis was performed at the National Institute for Environmental Studies, and they detected H5N1 highly pathogenic avian influenza virus (HPAIV). This is the first case of HPAIV detection in wild birds in this season. Since 2004, when the H5 HPAIV was first reported in Japan, this is the earliest case of the virus being detected in wild birds.
The National Agriculture and Food Research Organization (NARO) conducted virus isolation from specimens derived from the peregrine falcon and whole genome sequencing of this isolate (designated as Kanagawa strain). From the phylogenetic analysis of the eight gene segments, it was revealed that all segments of the Kanagawa strain were closely related to the 2020-2021 winter European isolate HPAIV (20E) (H5N1 subtype) that caused outbreaks in Japan in the 2021/2022 season. In addition, the Kanagawa strain does not contain any amino acid mutations which confer resistance against neuraminidase inhibitors and viral RNA polymerase inhibitors. Amino acid mutations which increase the infectivity in mammals were not confirmed.
At the end of September, which is early for the arrival of migratory birds in Japan, HPAIV infection cases were confirmed in wild birds in Japan, and also HPAI outbreaks have occurred in poultry from late October. Therefore, an increased alert is required against the virus introduction to poultry farms from now on.