Definition and management of the close contacts with Middle East respiratory syndrome cases: Reflection and lessons in 2015 Korean outbreak

Middle East respiratory syndrome (MERS) is an emerging zoonosis caused by the novel MERS corona virus isolated in 2012. Most MERS cases have been reported from Arab countries of the Middle East, including Saudi Arabia, United Arab Emirates, Qatar, and Jordan. There have been a few imported cases in many countries, but the exception is Korea, which reported 186 confirmed cases originating from one imported case in a two-month outbreak in 2015. There are many lessons to be learned from the MERS outbreak in Korea, among them, management of contacts. The definition of "close contact" used by the Korean Centers for Disease Control and Prevention (KCDC) for MERS response was not clear and not compatible with the definition of the World Health Organization. This incorrect definition allowed the KCDC make serious mistakes in contact tracing and management in the early epidemic stage of MERS. After the rapid expansion of the outbreak, the KCDC redefined a "close contact" according to the definition of the US CDC. The total number of close contacts was 16,693 in this outbreak, and they were all forced to conduct a self-quarantine for 14 days after the last contact with a MERS patient. It was not clear whether self-quarantine of close contacts was effective to control the outbreak. Given the lack of prepared guidelines or a social support system for them, these measures for the massive number of asymptomatic contacts caused a great deal of confusion in the field A clear response guideline is needed for contact management based on robust evidence from this MERS epidemic in Korea.