More than 680 people in South Korea have been placed in isolation after coming into contact with those infected with a virus that has killed hundreds of people in the Middle East.
The health ministry said three more people in South Korea have tested positive for Middle East Respiratory Syndrome, bringing to 17 the total number infected with the disease in the country.
Ministry officials said 682 people who had close contact with the patients, such as their family members and their medical staff, have been isolated at their homes or in state-run facilities.
The virus in South Korea has been largely limited to medical staff who treated the first patient and who stayed at the same hospital with him, as well as his family members.
In addition to the 17 cases of Mers in South Korea, the son of one of the patients became China's first case of the virus last week after travelling to the country despite being told by doctors to cancel his trip.
MERS was discovered in 2012 and has mostly been centred in Saudi Arabia.
It belongs to the family of coronaviruses that includes the common cold and Sars, and can cause fever, breathing problems, pneumonia and kidney failure.
The virus is thought to be primarily acquired through contact with camels but it can also spread from human fluids and droplets.
There have been 1,167 cases of the virus worldwide and 479 of the patients have died, according to the European Centre for Disease Prevention and Control.