Two suspected cases of an unknown inflammatory syndrome in children in South Korea turned out to be Kawasaki disease, health authorities here said Wednesday, amid concerns that the disease may be linked to the novel coronavirus.

The two children -- a 4-year-old girl and an 11-year-old boy -- were reported in Seoul last month for the first time for the disease, named Multisystem Inflammatory Syndrome in Children (MIS-C). They have recovered from the disease.

The two children were confirmed to have suffered from the rare Kawasaki disease, a syndrome of unknown cause that results in a fever, according to the Korea Centers for Disease Control and Prevention (KCDC). The disease occurs in 1 in 10,000 children under the age of 5.

"Both patients tested negative for COVID-19, and there are no particular factors to suspect the two children were exposed to the virus," KCDC Director Jeong Eun-kyung said in a daily briefing, adding the diagnosis was made in discussion with an advisory panel.

The symptoms of MIS-C include inflammation of the blood vessels, swollen hands and feet, vomiting, abdominal pain and diarrhea, which are similar to those of the Kawasaki disease,

There have reportedly been several more suspected MIS-C cases in the country, but the KCDC said they are highly unlikely to be the syndrome.

"The KCDC will continue to monitor other possible MIS-C cases from both home and abroad," Jeong said.

The boy, after entering from the Philippines in early March, showed symptoms of fever in late April before being hospitalized for rash and diarrhea. He was discharged on May 11.

After showing fever on May 12, the girl was admitted to a hospital on May 14, the KCDC said. She was released after making a full recovery on May 30.

The KCDC published a case definition for the disease. Children and adolescents under 19 show symptoms of a fever of 38 C or above lasting 24 hours or longer, with inflammation and multisystem (two or more) organ involvement in severe clinical condition requiring hospitalization.

No other pathogenic cause of inflammation should be found, and evidence of COVID-19 infection, or history of COVID-19 exposure within four weeks prior to the onset of illness, should be found, according to the KCDC.

MIS-C first emerged in Britain in late April. Hundreds of children in other parts of Europe, North America and Asia have since been treated in hospitals, with some cases leading to death.

The World Health Organization said MIS-C may be connected to the COVID-19 virus. (Yonhap)