Authorities have raised the nationwide crisis alert level for African swine fever to “serious” after the presence of the highly contagious viral disease was confirmed far from the inter-Korean border, where cases were previously concentrated.

A case was confirmed earlier in the week at a pig farm in Yeonggwang County, South Jeolla Province, following an earlier diagnosis in South Chungcheong Province in November.

Four cases in Gangwon and Gyeonggi provinces have been detected this month alone.

A new strain of the virus, prevalent in Southeast Asia, was also confirmed in South Korea for the first time.

Though wild pigs have traditionally been considered the No. 1 risk factor for African swine fever, the recent cases did not involve wild pigs, prompting authorities to look into other ways the virus may have spread.

Officials plan to disinfect pig farms nationwide and conduct environmental inspections, including inspections of farm workers’ homes.

African swine fever is frequently fatal in pigs, but the virus does not infect humans.