SEOUL, South Korea » It is the jewel of South Korea’s medical service: a 1,900-bed hospital of steel and glass owned by the famous Samsung conglomerate. It also is where a 35-year-old man whose symptoms were misdiagnosed as pneumonia languished for three days in an overcrowded emergency room and hallway, where he coughed up sputum teeming with the Middle East respiratory syndrome virus and exposed dozens.

Doctors of the renowned hospital, the Samsung Medical Center in Seoul, were the first to confirm the disease, known as MERS, in another patient a week earlier but failed to make the connection between the two cases. Investigators now say the misdiagnosed patient, awaiting a vacant bed in a general ward upstairs, wheezed and expectorated in common areas with no oversight, turning into a MERS "superspreader."

The mistakes by the Samsung Medical Center are now the focus of much that has gone wrong to escalate the MERS crisis in South Korea, the worst outbreak beyond Saudi Arabia, where the disease first appeared in 2012. As of Tuesday, nearly half of all 162 confirmed MERS cases in South Korea have been traced to Samsung, historically regarded as the nation’s best hospital.

Several hundred of its patients are under quarantine in the hospital or elsewhere, either because their infections have been confirmed or they are under observation for symptoms. Nearly 300 of its 3,900 medical and other staff members are under similar quarantine. Other hospitals have refused to accept patients from Samsung for fear of infection. By Sunday, it stopped taking new patients as it struggled to prevent the virus from further spreading beyond its gleaming compound.

"We offer our deep apologies to all MERS patients and those quarantined because of our employees," said Song Jae-hoon, the medical center president, bowing before television cameras.

Until now, Samsung’s reputation for quality had gone unchallenged. South Koreans looked no further than its list of patients: Lee Kun-hee, the country’s richest man and the chairman of the Samsung conglomerate, has been hospitalized there, in a 20th-floor VIP room, since his heart attack last year.

Nobody was surprised when Samsung diagnosed the country’s first case of MERS on May 20, attributing the discovery to its medical skills.

Calling Samsung a general hospital hardly explains its place in South Korea’s system.

In South Korea, when a parent gets sick, it is widely considered a filial duty for the children to mobilize all connections to secure a bed in Samsung or at a few other mega-hospitals, including one run by another family-controlled conglomerate, Hyundai, that they believe provide the best care.

When that strategy fails, patients are often taken into the hospitals’ emergency rooms, where they can wait for days for a bed in a general ward.

The Samsung hospital beds were usually filled, with 1,800 patients, and a long waiting list. Each day, 8,500 outpatients passed through.

But it was not just the fame of Samsung that attracted patients. Medical service is so affordable under the country’s universal medical insurance system that "there is no threshold at hospitals," said Kwon Jun-wook, a senior Heath Ministry official.

"Patients go to hospital as if they go shopping," Kwon said, referring to the practice of hospital hopping to get a second opinion or to get a referral to a mega-hospital, some of them with more than 2,000 beds.

Low medical fees also mean that hospitals must treat as many patients as possible to stay profitable. The big hospitals get more crowded as family members and private nurses they hire stay with patients. It is also important to social etiquette for South Koreans to visit hospitalized relatives, friends and colleagues, often with gifts like fruit boxes. Church members cluster around a patient’s bed, praying and singing.

The overall scene looks, as Koreans like to say, like a "flea market."

It is this overcrowded hospital condition that a World Health Organization mission said had made the otherwise modern South Korean hospitals particularly vulnerable to MERS. All those in the country who have the virus were infected in hospitals. Of them, 65 were relatives, friends or family-hired caretakers who contracted the disease while they were visiting or looking after hospitalized patients.

"The Samsung Medical Center is a national hospital in the sense that there are no regional boundaries in medical service in the country and everyone wants treatment there," said Kim Woo-joo, head of the Korean Society of Infectious Diseases. "The MERS outbreak was a stress test of our medical system, revealing its problems."

At Samsung, the system began unraveling when the 35-year-old man, whom investigators called Patient No. 14, arrived at its emergency room on May 27, a week after Samsung had discovered the first case.

Patient No. 14 had been infected by the first patient when both were in the same hospital south of Seoul in mid-May. But neither he nor Samsung doctors had any clue he was infected. Unlike the first case, he had no record of having visited the Middle East.

Samsung doctors diagnosed his case as pneumonia. But with no room in wards upstairs immediately available, he waited in the overcrowded emergency room for three days and sometimes loitered outside, investigators say.

It was not until May 29, when the Korean Centers for Disease Control and Prevention told them about the man’s possible link to the first case, that the emergency room doctors were alarmed, according to Samsung officials. By then, the man had become the biggest "superspreader" in the outbreak, infecting people in South Korea’s best hospital.

"It’s the nation that was penetrated," Chung Doo-ryeon, a Samsung doctor, responded during a parliamentary hearing last week, when lawmakers criticized the hospital for failing to control the outbreak. But blunders continued.

After Patient No. 14 tested positive on May 30, the hospital listed 893 people who may have come in contact with him in the emergency room, and placed them in quarantine or in self-isolation at home. But it failed to trace many visitors who had been in the room.

About half of the 80 cases that were traced to the Samsung hospital were found outside that list. Not bound by quarantine, they had gone about their lives, riding subways and visiting saunas. Some visited other hospitals when fever and other symptoms occurred. A Samsung doctor continued to work until he developed symptoms last week. An employee at Samsung carried 76 patients, some in wheelchairs, before he tested positive on Friday.

The breach in the quarantine at Samsung complicated the national battle against the disease.

So far, a total of 162 MERS cases have been found in 13 hospitals, including 20 deaths. But before the disease was diagnosed, the patients also passed through 70 other hospitals, raising fears that they may have infected people there. In some train stations, the local authorities have used heat-detecting cameras to stop potential MERS carriers from entering their towns. More than 6,500 people are in quarantine or in self-isolation at home, many of them after visiting the Samsung hospital.

"What pains us the most is our failure to contain Patient No. 14 at the Samsung hospital," said Kwon Deok-cheol, a senior official at the government’s MERS response headquarters.

Kwon said that the government planned to overhaul the country’s "hospital culture," such as unrestrained visits. But critics also blamed a "Samsung-style management" for the crisis.

The mass-circulation daily Chosun Ilbo said of Samsung Medical Center in an editorial this week: "It’s fair to say that their tendency to put profit and efficiency before public health prevented them from taking more decisive pre-emptive steps to contain the virus."

The Samsung conglomerate, the biggest among the enormous South Korean corporate empires that have been compared to "tentacles of an octopus," moved into the hospital business when it opened the Samsung Medical Center in 1994. Opening a modern hospital was said to reflect the wish of Lee, the conglomerate’s chairman, who used to travel to the United States for cancer treatment.

© 2015 The New York Times Company