More than 680 people in South Korea have been placed in isolation after coming into contact with Middle East Respiratory Syndrome (MERS) patients. Health officials said on Monday that they have placed 682 people on MERS watch list, a massive hike from its watch list of 64 people in May month.

A 58-year-old woman who interacted with a MERS patient died of respiratory failure on Monday, the health ministry officials said, according to the Korea Herald. The officials, however, said the government is in the process of finding out if she had been infected with MERS.

South Korea reported three more confirmed cases of infections as the number of infected patients reached 18 in just over 10 days, Reuters reported. With three new cases, South Korea has surpassed Qatar as the country with the fourth-most MERS cases in the world. All 18 patients have been infected from a 68-year-old man, who was diagnosed after returning from Bahrain via Qatar on May 20.

Yonhap news agency reported that government is going to place a temporary ban on people exposed to the MERS from leaving country after a South Korean man, despite having possible MERS symptoms, left for China last week. The 44-year-old man has been put in isolation at a Chinese hospital after diagnosed with disease.

South Korean President Park Geun-Hye reportedly scolded health officials over poor handling of the situation.

"The initial response to MERS... was insufficient," Park said in an official meeting, according to the AFP.

"We must find the reason for the high rate of transmission unlike in the cases of other countries," she said, according to Reuters.

Park's remarks came a day after country's Health Minister Moon Hyung-Pyo apologized for underestimating the initial threat of the MERS.

"This week will become a critical crossroads over whether MERS will continue to spread or subside," Moon said in a meeting of party officials in Seoul, according to Yonhap news agency. "I am very sorry for worrying citizens and causing them anxiety," he said.

MERS is a viral respiratory illness first identified in humans in 2012. There is no vaccine or treatment. Twenty three countries have been affected by the virus with most cases in Saudi Arabia. The South Korean outbreak is largest among 23 affected countries outside the Middle East, according to the AFP.

A WHO statement on Sunday said that the organization has not placed any travel or trade restrictions. At least 427 MERS-related deaths have been reported worldwide.