Japan has seen an unusually high number of avian influenza outbreaks this season, raising fears that the number of birds culled to prevent the disease from spreading could hit a record high for a single season.

Infections of the highly pathogenic bird flu virus have been breaking out at poultry farms and elsewhere across the country.

As of Wednesday, about 7.3 million birds, including chickens, had either been destroyed, or were supposed to be destroyed.

If infections keep spreading at the current rate, the number of birds destroyed may surpass the record of roughly 9.87 million set in the season from 2020 to 2021.

Hokkaido University avian flu expert Professor Sakoda Yoshihiro said infected migratory birds had begun arriving in Japan by late September, the earliest on record.

Sakoda said the birds have reached various locations around Japan, spreading the virus on an unprecedented scale.

He said the movement of migratory birds is transferring the virus to crows and other birds, allowing the virus to keep spreading until spring.

Sakoda said the bird flu season is still in its first half, and the number of outbreaks at poultry farms and elsewhere will likely remain very high for some time. He called on workers at such farms to take thorough anti-infection measures.