Passengers wearing masks to prevent contracting Middle East Respiratory Syndrome (MERS) sit inside a train in Seoul, South Korea, June 5, 2015. South Korean authorities squabbled on Friday over their handling of an outbreak of Middle East Respiratory Syndrome, as a fourth person died and five new cases were reported. REUTERS/Kim Hong-Ji

Airport staff wait for arriving passengers for a temperature check at Hong Kong Airport in Hong Kong, as a cautionary measure against MERS, June 5, 2015. REUTERS/Bobby Yip

Taipei mayor Ko Wen-je looks at a negative pressure isolation room (shown on the monitor) during a drill, as part of preparations in the event of an outbreak of MERS, at the Taipei City Hospital Chunghsin Branch in Taipei, Taiwan, June 4, 2015. REUTERS/Pichi Chuang

A health worker with protective suits sitting with people (R) who came into close contact with a South Korean MERS patient arrive at Lady MacLehose Holiday Village in Sai Kung, where they will spend two weeks in quarantine, in Hong Kong, May 30, 2015. REUTERS/Tyrone Siu

A Chinese tourist wearing a mask to prevent contracting MERS poses for photographs as men wearing traditional dress perform the daily reenactment of the changing of the Royal Guards, at the main entrance of the Gyeongbok Palace in central Seoul, South Korea, June 5, 2015. REUTERS/Kim Hong-Ji

Passengers wearing masks to prevent contracting Middle East Respiratory Syndrome (MERS) at Incheon International Airport in Incheon, South Korea, June 2, 2015. REUTERS/Kim Hong-Ji

Passengers wearing masks to prevent contracting Middle East Respiratory Syndrome (MERS) walk past a thermal imaging camera at Incheon International Airport in Incheon, South Korea, June 2, 2015. REUTERS/Kim Hong-Ji

Hospital workers stand in front of a quarantine area set up at a hospital in Seoul, South Korea, June 2, 2015. REUTERS/Kim Hong-Ji

A flight passenger from Busan, South Korea, receives a temperature check upon her arrival at Hong Kong Airport in Hong Kong, June 5, 2015. REUTERS/Bobby Yip

A medical personnel in a protection suit poses in front of an ICU room as she briefs the media, at a hospital where a South Korean MERS patient is being quarantined and treated, in Huizhou, Guangdong province, China, June 1, 2015. REUTERS/China Daily

People who came into close contact with the South Korean MERS patient arrive at Lady MacLehose Holiday Village in Sai Kung, where they will spend two weeks in quarantine, in Hong Kong, China May 30, 2015. REUTERS/Tyrone Siu

Security personnel adjust their masks outside an ICU room at a hospital where a South Korean MERS patient is being quarantined and treated, in Huizhou, Guangdong province, China, June 1, 2015. REUTERS/Chi

A police with mask stands guard outside Lady MacLehose Holiday Village in Sai Kung, where people who came into close contact with the South Korean MERS patient will spend two weeks in quarantine, in Hong Kong, May 29, 2015. REUTERS/Tyrone Siu

A boy wearing a mask to prevent contracting MERS walks past a thermal imaging camera at Incheon International Airport in Incheon, South Korea, June 2, 2015. REUTERS/Kim Hong-Ji

A quarantine officer checks the body temperature of a passenger as they walk past a thermal imaging camera at Incheon International Airport in Incheon, South Korea, June 2, 2015. REUTERS/Kim Hong-Ji

Passengers wearing masks to prevent contracting MERS wait for train at Incheon International Airport in Incheon, South Korea, June 2, 2015. REUTERS/Kim Hong-Ji

Passengers wearing masks to prevent contracting MERS walk past a thermal imaging camera (unseen) at Incheon International Airport in Incheon, South Korea, June 2, 2015. REUTERS/Kim Hong-Ji

Passengers wearing masks to prevent contracting MERS gather upon arrival at Incheon International Airport in Incheon, South Korea, June 2, 2015. REUTERS/Kim Hong-Ji

Passengers wearing masks to prevent contracting MERS walk past a thermal imaging camera (not pictured) at Incheon International Airport in Incheon, South Korea, June 2, 2015. REUTERS/Kim Hong-Ji

Medical personnel walk past inside the door of an ICU room at a hospital where a South Korean MERS patient is being quarantined and treated, in Huizhou, Guangdong province, China, June 1, 2015. REUTERS/China Daily

Policemen wearing mask sit in a tent outside Lady MacLehose Holiday Village in Sai Kung, where people who came into close contact with the Korean MERS patient will spend two weeks in quarantine, in Hong Kong, May 30, 2015. REUTERS/Tyrone Siu