SEOUL/SEJONG, June 13 (Yonhap) — The World Health Organization (WHO) warned Saturday that South Korea may have to brace for a drawn-out battle against Middle East Respiratory Syndrome (MERS), saying that its outbreak is “large and complex.”

The warning comes as the daily tally of confirmed MERS cases in South Korea shows signs of a rebound. A dozen new infections were found on Saturday, raising the total to 138, The death toll stood at 14.

More alarming was the first report in the country of a fourth-phase infection despite the government’s all-out efforts to curb the spread of the MERS coronavirus.

The 12 new patients include an ambulance driver who last week transported two people diagnosed with the potentially deadly virus in the third-phase endemic.

After a weeklong on-site review, the WHO predicted additional infections.

“Because the outbreak has been large and is complex, more cases should be anticipated,” Keiji Fukuda, the WHO’s assistant director-general of health security, said at a press conference in the administrative town of Sejong, some 130 kilometers south of Seoul.

He was briefing reporters on the results of the agency’s joint study with a South Korean team led by Lee Jong-koo, head of the Center for Global Medicine, at Seoul National University.

Fukuda said more cases are expected although there is no indication of any mutation of the virus in South Korea, saying it has spread in a similar pattern to previous outbreaks in the Middle East.

Lee agreed that it’s still too early to declare a “complete end” to the fight against MERS.

“It is anticipated to take more time,” he said.

However, Lee, a medical doctor himself, said the outbreak cannot be viewed as a national emergency. Describing MERS as a form of cold, he said public fear is over-rated.

“Initially it was thought that MERS brings about pneumonia, but in most cases, symptoms are similar to those of the common cold,” he said.

The fatality rate of MERS has been estimated at 30-40 percent, but in South Korea it hovers at 10 percent, with most people who succumb to the MERS virus already having underlying medical conditions such as weak respiratory systems, hypertension, diabetes, heart and lung diseases and cancer.

According to government health officials, a 67-year-old woman who died overnight after being infected with MERS had already suffered from thyroid gland problems and high blood pressure which were apparently worsened by the MERS virus.

Related to treatment of other patients, officials said that a medical doctor and a policeman who did not suffer from any health problems before getting infected, may have experienced a “cytokine cascade” condition. The cascade occurs when the body’s immune system over-reacts to a pathogen infection and attacks healthy organs by mistake. In serious cases, patients with this condition can die.

Both the doctor and police officer are listed in serious condition.

An official added that doctors had injected both with blood plasma from a person who recovered fully from MERS, in the hope this may help the two who are both 35 years old.

“So far the blood plasma injections have not caused a change in their condition,” the insider said.

Meanwhile, Samsung Medical Center in Seoul announced it will partially suspend operations and not receive outpatients after a joint government task force charged with containing the outbreak, warned there is a chance that the virus may spread again at the hospital.

The task force said an employee responsible for moving patients tested positive for the MERS-inducing virus, and urged the medical center to respond quickly and check all people that came in contact with the infected person.

The hospital said the special measure is being taken to prevent further spread of MERS. It said access to the emergency room will be restricted and people will be barred from visiting patients.

“With the exception of critical cases, surgery will be halted as well,” a hospital official said. He added that the hospital fully supports the government’s effort to contain MERS.