SEOUL, June 8 -- South Korea on Monday identified 23 new contagions with the Middle East Respiratory Syndrome (MERS), increasing the total number to 87 while deaths from the viral disease rose to six as one more death was reported.

Twenty-three infections found Monday alone were the largest daily increase since the first case was identified on May 20, according to the Ministry of Health and Welfare. The total number surged to 87, making the country the world's most MERS-contagious except Saudi Arabia, where more than 1,000 cases were identified.

The 80-year-old infectee passed away early in the morning after being hospitalized at Daecheong Hospital in the country's central city of Daejeon. The death toll rose to six, sending the fatality rate to 6.9 percent.

The health ministry said 10 more infectees have been in serious conditions, leaving a room for more deaths from the disease. All the deceased were the elderly mostly in their 70s and 80s having suffered from other illnesses.

Among the 23 new cases, 17 people were infected from the 14th patient at the Samsung Medical Center in Seoul for three days from May 27. The total number infected at the hospital soared to 34.

The 14th infectee was estimated to have transported the virus from the Pyeongtaek St. Mary's Hospital, where the first patient was hospitalized for three days from May 15, to the Samsung Medical Center as he traveled to Seoul by bus from the hospital in Pyeongtaek, some 60 km south of Seoul.

Kwon Joon-wook, head of the central headquarters for the MERS management, told a press briefing that the first phase of epidemic seemed to have ended in the Pyeongtaek hospital because any single case wasn't added from the hospital Monday.

Kwon said the second phase at the Samsung Medical Center was expected to calm down soon, but he expressed deep worries about the 76th patient who contracted the virus from the 14th patient for two days from May 27 at the Samsung Medical Center.

The 75-year-old woman, tested positive Monday, visited emergency rooms of the Gangdong Kyunghee University Medical Center and the Konkuk University Medical Center before being put under quarantine. The two hospitals are located in Seoul.

Those who visited the two hospitals and were suspected of MERS infection totaled 386 people, now being placed under quarantine.

The health authorities asked people visiting the two hospitals to be put under self-quarantine after reporting their visit to the authorities, not to visit other hospitals.

The 81st patient, confirmed positive Monday, went to the southern port city of Busan after visiting the Samsung Medical Center, boosting fears that the MERS might have spread nationwide.

A 72-year-old woman, tested positive Sunday, moved back to her home in Sunchang, North Jeolla Province after being discharged on May 21 from the Pyeongtaek hospital where the patient zero stayed. The whole village has been under quarantine to prevent further spread.

As of Monday, 2,508 people have been under quarantine, and 583 people were released from the isolation. A 50-year-old infectee, a doctor who treated the first patient, was discharged from a hospital, sending the total hospital discharge to two.

The remaining six new cases came from the 16th patient at two hospitals in Daejeon, a city at the center of South Korea.

Among them, four people contracted the virus at Daecheong Hospital, with the other two taking the contagion at Konyang University Hospital. Those infected at the two hospitals increased to seven respectively.

The MERS is a respiratory illness caused by a new type of corona-virus, similar to the SARS virus that killed more than 770 people worldwide following a 2003 outbreak. There is no known vaccine or treatment for the MERS, of which fatality rate reaches 40.7 percent.

The first MERS case was spotted in Saudi Arabia in 2012. The World Health Organization has reported more than 1,000 cases of MERS globally and more than 400 deaths.