South Korea confirmed nine more cases of the Middle East Respiratory Syndrome on Saturday, bringing the total number of people infected with the disease to 50.

Five of them were infected with MERS after visiting Samsung Medical Center in southern Seoul, where a doctor was recently diagnosed with the illness, according to the health ministry.

Another three were patients and medical staff at Saint Mary Hospital in Pyeongtaek, south of Seoul, where the first MERS case originated weeks ago.

The total number of MERS infections has reached 50, with four deaths, since the first outbreak on May 20.

MERS is a viral respiratory illness that had a very high fatality rate of over 40 percent globally before the outbreak in South Korea, according to the Korea Centers for Disease Control and Prevention.

Most people infected with MERS develop severe acute respiratory illness, including a fever, cough and shortness of breath. There currently is no vaccine or treatment for the disease.

The health ministry said it agreed with local governments to disclose other MERS-affected hospitals in order to take preemptive measures to tackle the fast-spreading respiratory illness.

The South Korean authorities identified Pyeongtaek St. Mary's Hospital on Friday on rising public demand for sharing facilities'

names. They had refused to share the names of hospitals for more than two weeks, citing "unnecessary fear and stigmatization."

The move came after Seoul Mayor Park Won-soon held a midnight press conference to complain of the authorities' lax disease management and said he would now take charge of efforts to deal with MERS in Seoul.

Park disclosed that a Samsung Medical Center doctor who has since been diagnosed with MERS allegedly had direct and indirect contact with over 1,500 people before his infection was confirmed.

Meanwhile, the health ministry said that the MERS virus spreading in South Korea has not mutated and showed similar genomic sequences with the contagion discovered in Middle Eastern countries.

The fast pace of MERS proliferation in South Korea has raised questions among foreign experts about whether the virus has undergone changes that could make it more infectious.

"The Korea National Institute of Health (KNIH) brought in such results after doing a culture test on the MERS virus gathered from a local patient and analyzing its full genomic sequence," said the ministry in a press briefing.

The KNIH did the joint research with a local virology society, the U.S. Centers for Disease Control and Prevention and other foreign institutions to find out whether a gene mutation happened in South Korea.

The ministry said the virus from the South Korean patient had a

99.55 percent similarity with a virus sample from a Saudi Arabian stored by the U.S. National Institute of Health in 2012.

"South Korea's weather is more favorable for the survival of the MERS virus than in the Middle East," said an official from the ministry. "In terms of virology, the virus here is the same." (Yonhap)