Despite the government’s stepped up quarantine measures to contain the outbreak of bird flu, a highly pathogenic aviation influenza virus appeared to be spreading rapidly throughout the nation.

Following new reported cases in Yangju in Gyeonggi Province and Sejong in South Chungcheong Province over the weekend, some 200 chickens were found dead on Monday morning in Eumseong, South Chungcheong Province, quarantine authories said.

So far, a total of 15 poultry farms were confirmed with AI cases, while eight other farms are under examination.

A total of 627,812 animals including chickens and ducks have been slaughtered at some 45 farms, since Nov. 16, when the first outbreak was reported at a chicken farm in Haenam, South Jeolla Province.

The Korea Centers for Disease Control and Prevention said that more cases are being examined as wild bird infections were reported around the western coastal areas and throughout Gyeonggi Province, the country’s largest poultry production base.

Authorities see migratory birds as the source of the H5N6 virus outbreak here as there have been no reports of infections through the movement of people or livestock.

This is the first time that South Korea has reported an outbreak of the H5N6 strain of bird flu.

In neighboring China, there have been 16 cases of human infections of H5N6 since 2014. Ten of those infected died.