A couple wearing masks to prevent contracting MERS looks at each other as they ride on an escalator in Seoul, South Korea, June 11, 2015. REUTERS/Kim Hong-Ji

An employee from a disinfection service company sanitizes an empty classroom of an elementary school in Seoul, South Korea, June 11, 2015. REUTERS/Kim Hong-Ji

Tourists wearing masks to prevent contracting MERS look at a tour map of Seoul at Myeongdong shopping district, in central Seoul, South Korea, June 10, 2015. REUTERS/Kim Hong-Ji

Workers in full protective gear disinfect the interior of a subway train at a Seoul Metro's railway vehicle base in Goyang, South Korea, June 9, 2015. REUTERS/Kim Hong-Ji

An elementary school student wearing a mask to prevent contracting MERS, receives a temperature check at an elementary school in Seoul, South Korea, June 9, 2015. REUTERS/Kim Hong-Ji

Tourists wearing masks to prevent contracting MERS are reflected on mirrors in Seoul, South Korea, June 8, 2015. REUTERS/Kim Hong-Ji

A woman wearing a mask to prevent contracting MERS walks out from a clothing shop at Myeongdong shopping district in central Seoul, South Korea, June 11, 2015. 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

Passengers wearing masks to prevent contracting MERS sit inside a train in Seoul, South Korea, June 5, 2015. REUTERS/Kim Hong-Ji

A worker in a full protective gear disinfects the interior of a subway train at a Seoul Metro's railway vehicle base in Goyang, South Korea, June 9, 2015. REUTERS/Kim Hong-Ji

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

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

Military officials wearing masks as a precaution against contracting MERS check the body temperature of visitors sitting inside their car at the entrance of the Defense Ministry in Seoul, South Korea, June 9, 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

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

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

A military policeman wearing a mask as a precaution against contracting MERS stands guard at the entrance of the Defense Ministry in Seoul, South Korea, June 9, 2015. REUTERS/Kim Hong-Ji