South Korea said Tuesday it has decided to lower the alert level for highly pathogenic avian influenza as no new cases have been reported for more than a month.

The alert level for the animal disease was lowered to "blue" from the previous "red" Tuesday, according to the Ministry of Agriculture, Food and Rural Affairs.

South Korea operates a four-tier alert level system for animal diseases, namely blue, yellow, orange and red. Blue is the lowest level, while red is the highest.

"Migratory birds have mostly moved back to their northern habitats, and no new cases of highly pathogenic strains of bird flu from the wild have been reported since March 30," the ministry said in a statement.

There have been no new cases of the H5N8 strain of avian influenza traced to poultry farms since April 6.

A total of 109 farm-linked cases were reported since November last year, when the authorities issued the red alert.

The number of bird flu cases from poultry farms came to 383 over the same period during the previous wave, which ran between 2016 and 2017.

The country said it was able to reduce the damage to local farms as it culled birds within a 3-kilometer radius of infected farms during the early stage of the outbreak. The regulation was later revised to a 1-kilometer radius in February.

During the 2016-2017 wave, South Korea only destroyed birds within a 500-meter radius.

South Korea said it will continue to roll out preventive measures at local poultry farms regardless of the alert level. (Yonhap)