South Korea's health authorities confirmed five additional cases of influenza A on Wednesday, raising the number of confirmed cases to 53.

According to the nation's Ministry for Health, Welfare and Family Affairs, the newly confirmed patients, all of whom having South Korean passports, have been placed at state-designated hospitals for close observation and treatment.

Of the five people, three were returning from trips to the United States, with one from Australia and the other from the Philippines.

It is the first time for the nation to confirm a traveler from Australia to be infected with the flu.

In addition, as a 38-year-old man included in the new list is found to be a coworker of an earlier confirmed patient, authorities have become concerned that he may have contracted the disease through person-to-person contact.

With the recent cases, South Korea's A/H1N1 flu confirmation toll stands at 53 as of Wednesday afternoon.

Of the total cases, seven still remain under close observation in isolated hospitals with the rest being released in good health.

No death case has been reported in South Korea due to the A/ H1N1 flu.

(Xinhua News Agency June 10, 2009)