BEIJING, June 16 -- Infections with the Middle East Respiratory Syndrome (MERS) abated in South Koreaas four more cases were added on Tuesday, while three more deaths were reported.

By far, the viral respiratory illness has killed 19 people and infected 154 people in South Korea.

While medical experts had maintained that MERS was deadly mostly to the elderly and those who already have health problems, one of the four newly deceased was a 49-year-old patient, the youngest person that has died from the illness in South Korea, according to the Ministry of Health and Welfare.

Moreover, four out of the 19 who died from MERS had no health problems before they were infected with MERS.

Seoul's Samsung Medical Center remained a major source of MERS infections, as three of the four new patients were infected while visiting the hospital.

However, the health ministry is confident that the MERS outbreak in South Korea will end in late June unless any "super spreader" emerges further.

Kwon Jun-wook, director general of the health ministry's public health policy, held a press conference on Monday with foreign correspondents in Seoul, saying that the last day of the 14-day latent period among potential super spreaders will be June 27. If no infection cluster is added by that day, the MERS outbreak could be viewed as coming to an end.

The MERS spread was originally expected to be contained by June 12, but new cases would continue to be added "sporadically" by the end of this month as new potential "super spreaders" infecting more than eight people were discovered.

The patient zero, also called index case who began to show MERS symptoms from May 11, was quarantined from May 20. The last day of his 14-day incubation period was June 3, but since the day, another infection cluster, or a massive number of contagions, was caused by the 14th patient, who was infected by the first patient.

The 14th patient alone infected more than 70 people at the Samsung Medical Center in Seoul, which was partially closed last weekend for its failure to control and prevent the viral disease within hospitals. The index case infected 37 people at St. Mary's Hospital in Pyeongtaek, some 60 km south of Seoul.

The second wave of epidemic was originally forecast to ease from June 12 , which was the last day of the two-week latent period for the 14th patient. Though the second wave showed calming signs, there were still concerns that potential super spreaders might further appear.

"The first wave (from the patient zero) ended, and the second wave (from the 14th patient) showed calming signs," Kim Woo Joo, head of the Korean Society of Infectious Diseases who's now working in the health ministry to contain the outbreak, told reporters.

Kim said nearly 90 percent of MERS infections here came from three super spreaders, including the 16th patient, noting that the health authorities have been focusing on preventing another super spreader from emerging.

The infectious disease expert said that there is no evidence of human-to-human transmission in the community in South Korea as seen in Saudi Arabia, adding that there have been only cases of transmission within hospitals and between hospitals.

Chinese and American scientists have jointly developed a new antibody against the MERS virus.

Fudan University, which worked with U.S. National Institutes of Health to develop the antibody, said on Monday that tests on animals had yielded "very effective" results.

Jiang Shibo, who led the research team at Fudan, said the m336 antibody could neutralize MERS virus more effectively than other antibodies.

He said the m336 antibody treatment has proved more effective when coupled with a specific type of polypeptide.

Zhong Nanshan, a renowned Chinese respiratory expert, has called for an immediate clinical trial.