South Korea was struggling to contain the spread of highly pathogenic bird flu among local poultry farms as the number of such cases reached nearly 40 on Thursday, but the influx of migratory birds continued to strain the antivirus fight.

The latest highly contagious H5N8 strain of bird flu was found from a duck farm in Gimpo, just north of Seoul, on the previous day, according to the Ministry of Agriculture, Food and Rural Affairs.

Among the 37 farm-related cases reported so far, 10 came from Gyeonggi Province that surrounds Seoul, while South Jeolla Province accounted for nine.

The number of birds destroyed by local authorities reached 11.5 million as of Thursday. Birds within a 3-kilometer radius of infected farms are culled under the local quarantine law.

South Korea has also been experiencing an increase in the number of avian influenza cases among wild birds. So far, 45 cases have been reported from their habitats.

With migratory birds expected to fly into the country through early 2021, local authorities are vigilant over possible transmissions of the disease to the poultry farms. (Yonhap)