A 58-year-old woman who interacted with Korea’s first confirmed MERS patient died of respiratory failure on Monday evening, the Health Ministry said.

The government is in the process of finding out if she had been infected with MERS. According to local news reports, she was hospitalized on May 25 after experiencing shortness of breath. She died six days after.

Earlier on the day, Seoul said it was monitoring 682 people, a massive expansion from its watch list of 64 people announced last month, for possible infection of Middle East respiratory syndrome, after confirming the country’s 18th case. 

Those on the watch list have also been banned indefinitely from leaving the country, the government said. The announcement came shortly after Seoul’s recent failure to prevent the 10th MERS patient from going overseas to China on May 26. This left 165 passengers and crew members on board the same plane at potential risk of infection.

“We will put forth our best efforts to prevent any potential MERS patients from going overseas,” said Kwon Jun-wook, who leads the government’s special task force tackling MERS.

Among the 18 confirmed patients, five of them are in unstable condition, meaning they either have to rely on a ventilator to breathe or are experiencing kidney or other organ failures. A 71-year-old, who became the sixth confirmed MERS patient on May 28, is particularly at risk, as he had been suffering from a chronic kidney disease prior to being diagnosed with MERS, officials said.

The first confirmed patient, quarantined since he was diagnosed on May 20, had visited four medical clinics and hospitals over the course of 10 days prior to his diagnosis. He is currently believed to be the sole spreader of MERS in Korea. The 682 people to be watched include all health care workers and patients who were present when the first MERS patient either stayed or visited the four facilities.

Among the 682, about 35 percent are considered to be the most vulnerable -- those who are aged 50 or older and those who have chronic conditions such as diabetes, heart or kidney diseases.

Kwon said about 150 beds were currently available nationwide for patients who needed to be isolated.

“We can, of course, increase the number of hospital beds (with the right equipment),” he said.

Last month, the Health Ministry’s monitoring list omitted patients who did not share a ward with the first three confirmed patients but stayed in the same hospital, claiming MERS was less contagious than many other infectious diseases. The list then only contained close family members of the three patients, as well as health care workers who treated them.

Almost half of those infected by the first patient were not even included in the government’s initial monitoring list.

Among the 17 patients who are believed to be infected by “patient zero,” 15 were at the same facility as the 68-year-old, who was being treated there as an inpatient from May 15-17. Out of the 15, nine were staying there as inpatients. The facility, which has since been temporarily shut down, is the second of the four hospitals he visited or stayed at before being quarantined.

The remaining two patients are health care professionals who treated the first patient prior to his diagnosis, each at different medical clinics, on May 15 and 17, respectively.

The incubation period of MERS is considered to be from two to 14 days, and all those infected by the first patient were in contact with him from May 15-17.

As the first patient visited different clinics before his diagnosis between May 17 and 20, more people may be diagnosed this week, as the incubation period of those who may have been infected at the clinic lasts until Thursday.

As the nation continues to grapple with the spread of MERS, members of the government and the ruling party gathered for an emergency countermeasures meeting.

“This week is a crucial turning point in which the situation can either get better or worse,” said Rep. Won Yoo-chul, senior policymaker of the ruling Saenuri Party.

“The government must do everything it can this week to prevent a further spread of the disease, while making sure false rumors about the disease that make the public unnecessarily anxious don’t go viral.”

The party and the government also discussed the incident involving a live anthrax sample that was mistakenly sent to an American military base in Korea from the U.S.

“We are considering legal and institutional ways to regulate all potentially dangerous substances that arrive in Korea,” Won said.

“We’ll be discussing this issue at the Status of Forces Agreement meeting scheduled in July.”

By Claire Lee (dyc@heraldcorp.com)