South Korea on Monday recorded its worst day for Middle East respiratory syndrome since the outbreak began almost three weeks ago, as President Park Geun-hye’s government tried to allay panic and convince a skeptical public that it was on top of the situation.

A sixth person died of the virus, and it was confirmed in 23 more people — including a 16-year-old boy — on Monday, marking the biggest single-day jump in infections. With 87 cases, South Korea has overtaken the United Arab Emirates to become the second-worst-affected country after Saudi Arabia, where the virus emerged three years ago.

The spiraling health crisis — and the widespread perception that her administration has been slow and blundering in its response — has led to calls for Park to delay a trip to the United States, set to start Sunday. Her visit is scheduled to include talks at the White House with President Obama on June 16.

But Park’s spokesman said Monday that there was “nothing to announce” regarding her planned trip.

Park’s government — already struggling with public trust in the wake of the Sewol ferry disaster last year that killed more than 300 people — has been widely criticized for trying to keep key details from the public, especially by declining to name the hospitals where infected patients were treated.

Foreign tourists wear masks as a precaution against Middle East Respiratory Syndrome (MERS) on the Myeongdong, one of the main shopping districts, in Seoul. (Ahn Young-Joon/Associated Press)

“I think the spread could have been ended much earlier if we reacted more thoroughly in the initial stage. I feel very sorry about that,” Moon Hyung-pyo, the nation’s health minister, said at a news conference Monday.

As a World Health Organization team arrived in Seoul, he predicted that the outbreak had reached its peak. “It may hopefully go into a stable condition tomorrow or the day after tomorrow,” he said, according to a Yonhap News Agency report.

The respiratory virus, which appears to have jumped from camels to humans, arrived in South Korea last month in a 68-year-old man who had traveled to four Middle Eastern countries, and went to four hospitals upon his return to try to find out what was wrong with him.

Almost all the transmissions have occurred in hospitals where infected people were treated. A member of the South Korean air force who is stationed at an American military base in Osan, near one of the hospitals visited by “Patient Zero,” was infected after visiting the hospital for an Achilles tendon injury.

The sixth person to die from the virus was an 80-year-old man at a hospital in the central city of Daejeon.

The government finally gave in to public demands Sunday for a list of the 24 hospitals and clinics that had treated MERS patients after saying it would not name them partly to avoid hurting the hospitals commercially.

It turned out that 17 people were infected at the Samsung Medical Center, which is part of the Samsung business empire and is in the ritzy southern Seoul suburb of Gangnam.

The lack of transparency has led fearful South Koreans to remain behind locked doors — even though health authorities have said the virus is difficult to catch through casual contact.

Fears were fueled further when it emerged that a doctor who was infected with MERS attended a conference in late May with 1,565 other people. More than 2,300 people are now in quarantine, and the government is monitoring their cellphones to make sure they do not leave their homes. The incubation period ranges from two to 14 days.

The outsize reaction to the outbreak is largely linked to the government’s handling of it, analysts said.

“People panicked because of the uncertainty,” said Han Sung-hoon, a social scientist at Yonsei University. “Information access is a fundamental element in democracy. When this access was denied, people became more confused and concerned.”

Some lawmakers from both the ruling and opposition parties called on Park to delay her trip to the United States while the crisis continued.

Park’s job approval rating has dropped six points, to 34 percent, in a week, according to a Gallup Korea poll published last week.

Even before the MERS outbreak, Park was flailing. She has been hit by a series of scandals involving her top personnel, with a steady procession of prime ministers or candidates for prime minister having to stand down over allegations of financial and other wrongdoing.

She was widely criticized for her government’s handling of the Sewol ferry disaster in April 2014 and she was again criticized this year for traveling to South America on the anniversary of the crisis.

Scott Snyder, an expert on Korea at the Council on Foreign Relations, said the latest crisis to befall Park, coming in the middle of her five-year tenure, could limit her ability to make progress.

“The third year is the most important in terms of deliverables,” Snyder said. “If MERS cases continue to expand and rob her of her momentum once again, there is a possibility that she will be left with a meager set of accomplishments to claim during her presidency.”

Meanwhile, almost 2,000 schools have canceled classes. The streets of Seoul and the city’s subway cars are as empty as they are during Korean Thanksgiving, the biggest holiday of the year.

“I try not to leave the house unless I need to, and when I leave I always wear a mask,” said Cecilia Suh, whose face was covered with large sunglasses and a white mask as she made a rare trip out to have her cellphone fixed. “I don't use public bathrooms or take public transportation.”

Movie theaters, department stores and supermarkets are reporting a sharp drop in business. Many sporting events have been canceled or postponed.

Chun Sung-bae, who runs a cafe in the bustling Shinchon area of Seoul, said he was seeing 20 to 30 percent fewer customers. “Usually around this time of the day, we don’t have empty tables, but as you can see, there are many,” he said at 4 p.m. Monday. “I'm worried about how I’m going to pay this month’s rent if this condition continues.”

The Korea Tourism Organization said that more than 45,000 tourists from Asia had canceled planned visits to South Korea in the first week of this month, local broadcaster News1 reported.

Fifield reported from Tokyo.

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