South Korean health authorities confirmed Saturday that a South Korean woman living together with the fifth confirmed case has been infected with the new type-A influenza virus, as the sixth case in the nation.

    The 26-year-old woman resides in the same building as an American English teacher who was confirmed to be infected with the virus Saturday morning, said the Korea Centers for Disease Control and Prevention.

    Health authorities said they are working on tracking down about 70 individuals who came into contact with the American woman since she arrived in the country on May 16.

    Out of the 70, seven including the newly confirm case have been quarantined after showing apparent flu-like symptoms. Four have been classified as possibly being infected with type-A/H1N1 influenza and have been moved to a hospital in Seoul, while two others have already tested negative, the authorities said.

    The center said test results for the four possible patients will be disclosed on Sunday.

    The South Korean government has now confirmed six cases of the new virus -- four Koreans, one Vietnamese traveler and one American. Three South Koreans have all recovered from the disease after being treated with antiviral medication.

    Since the outbreak of the new flu virus was first reported in Mexico last month, Seoul has been stepping up efforts to stem the spread of the disease by intensifying monitoring of inbound travelers.