BANGKOK/SEOUL: One of Thailand’s leading hospitals, known for treating medical tourists, said on Friday it had received the country’s first case of Middle East Respiratory Syndrome (MERS), as authorities said it had taken nearly four days to confirm the illness.

Thailand said a 75-year-old businessman from Oman, who had travelled to Bangkok for medical treatment for a heart condition, had tested positive for MERS.

The announcement came just as an outbreak in South Korea that began last month and has infected 166 people, killing 24 of them, appeared to be levelling off.

The MERS outbreak appears to have begun subsiding in South Korea, as it reported one new case, the lowest rate of new infections in two weeks, the Health Ministry said on Friday.

The number of people in quarantine had fallen 12 percent from Thursday to 5,930, a day after Thailand reported Southeast Asia’s first case of the deadly virus since the South Korean outbreak.

The government of President Park Geun-Hye has come under attack for its inadequate initial response but World Health Organization (WHO) chief Margaret Chan expressed guarded optimism Thursday over South Korea’s ability to contain the outbreak.

She said Seoul was now “on a very good footing” after an initially slow response.

The high-end Bumrungrad Hospital, run by Thailand’s second-largest hospital operator, identified the first MERS case. The hospital in central Bangkok treats over a million patients a year, about half of them foreigners.