One new case of Middle East Respiratory Syndrome (MERS) was also announced, bringing the total number to 166, according to South Korea's Ministry of Health.
The number of people under quarantine in South Korea, both in their own homes or in quarantine facilities, declined from 6,729 to 5,930
The World Health Organization described the MERS outbreak as a "wakeup call," showing that outbreaks can happen anywhere.
The WHO has said that the number of new cases "appears to be declining" -- indicating that the outbreak could be slowing down. But it also warned that "all outbreaks are unpredictable" -- especially for new diseases that are not well understood.
This week, there had been a sign of a possible return to normalcy, as thousands of schools across South Korea re-opened after closures due to the deadly outbreak. But it came with heightened awareness; children's temperatures were monitored in classrooms and teachers warned students to practice personal hygiene and frequently wash their hands.
The WHO had recommended re-opening institutions last week because transmission of the virus had not been linked to schools. The MERS outbreak remains largely confined to health care settings.
23 now dead in South Korea
The outbreak has sparked international concern, stalled the nation's economy and resulted in over 100,000 canceled tourist visits to the country. Korea's department store sales tumbled 16.5% compared with the same period last year and retail shops also decreased 3.4%, according to the Ministry of Strategy and Finance.
The ongoing situation has put Korean authorities under scrutiny for their inability to contain MERS cases and President Park Geun-hye has seen her approval ratings plummet.
The spread of MERS in South Korea has remained within healthcare settings, but Dr. Keiji Fukuda, a WHO Assistant Director-General warned that transmission could occur outside of hospitals -- which has occurred before in the Middle East.
"Even given that possibility, right now we do not see any evidence of this virus causing sustained transmission in community or sweeping through," he said.
Efforts on MERS antibody
Researchers from the U.S. National Institutes of Health and China's Fudan University have been working on an antibody treatment that could fight MERS. An antibody is a protein that combats pathogens like viruses and bacteria.
The antibody treatment has only been through lab and animal tests so far and requires trials on humans before it could be available to MERS patients.
While the antibody, named m336, has been effective in animals, it has yet to be tested on MERS patients, said Professor Jiang Shibo from Fudan University. All U.S. drugs are required to have human trials, as there are treatments that work in animals but turn out to be ineffective in people.
The human trial process could take three to four years, but experimental treatments can be used if patients and the local government consent.
So far, m336 has been considered the most potent of several antibodies that could be used to fight MERS, according to a scientific summary published in the Journals Center for Cancer Research.
Saudi Arabia connection
Meanwhile, Saudi Arabia has recorded five cases of MERS in the past week, the official state-run Saudi press agency said Sunday, citing a weekly Ministry of Health statement. It included one death of a 73-year-old man who died in the city of Turaba and had a pre-existing condition.
The strain of coronavirus that causes MERS was first identified in 2012 in Saudi Arabia, according to the WHO.
The man believed to be "patient zero" in the current outbreak in South Korea visited Saudi Arabia in May, along with three other Middle Eastern countries. That 68-year-old patient went from facility-to-facility near or around Seoul before getting properly diagnosed. It triggered the hospital-based transmission of MERS in South Korea.
The South Korean outbreak is the largest outside of Saudi Arabia -- nearly 6,000 people remain in quarantine.
Gangnam hospital focal point in MERS outbreak
In Seoul, Samsung Medical Center -- one of the city's hospitals that has counted many of the nation's MERS cases among its patients and visitors -- announced Sunday that it will suspend all surgical procedures except for emergency surgery "to fully focus on responding to MERS."
More than 50 confirmed MERS cases have been traced back to the medical center, according to the center's website.
The medical center, located in Seoul's glitzy Gangnam district and considered one of the most prominent hospitals in the capital, issued an apology for its handling of MERS.
"We sincerely apologize with our heads bent to the people for causing great concern as Samsung Medical Center became the center (of) the spread of MERS," hospital President Song Jae-hoon said.