Story highlights

NEW: South Korea battles MERS with 3 deaths, 35 cases and 1,369 in quarantine

Extent of outbreak surprises experts, because South Korea's health care system is good and virus doesn't spread easily between humans

More than 700 South Korean schools shut to prevent infection

Hong Kong CNN —  

The World Health Organization warned that the MERS outbreak in South Korea is likely to grow, as the number of people under quarantine crept up to 1,369 on Wednesday.

The Korean Centers for Disease Control and Prevention confirmed five new cases – increasing the number of people with the disease to 35. These new cases were contracted within hospitals.

The MERS outbreak in South Korea is the largest outside Saudi Arabia.

The first South Korean case, concerning a man who returned to the country after traveling to Saudi Arabia, Qatar, the UAE and Bahrain, was reported on May 20. The person had not been ill during his travels, according to the World Health Organization.

More than 900 schools have shut to prevent the spread of the virus, according to South Korea’s education ministry.

The extent of the outbreak has taken many by surprise – mainly because the virus has not been shown to spread easily between humans and the health care system in the country is considered to be sophisticated and modern.

President Park Geun-hye acknowledged problems in the country’s early response earlier this week.

“Initial reaction for new infectious diseases like MERS is very important, but there were some insufficiency in the initial response, including the judgment on its contagiousness,” she said.

The virus acts like a cold and attacks the respiratory system, the CDC has said. But symptoms, which include fever and a cough, are severe and can lead to pneumonia and kidney failure.

MERS is in the same family of viruses as SARS (severe acute respiratory syndrome) as well as the common cold. However, MERS does not spread easily between humans – as far as scientists know at this point.

“So far, the virus has been circulating in humans for three years,” said Dr. Leo Poon, a virology expert at the School of Public Health at the University of Hong Kong, who worked on the SARS outbreak more than a decade ago. “We found little transmission in human. We know there is human-to-human transmission, but it’s not sustainable.”

Then why is it spreading in South Korea?

Since MERS, short for Middle East respiratory syndrome, was first reported in Saudi Arabia in 2012, international cases have largely been confined to travelers bringing the virus back to other countries and infecting one or two others