An Outbreak of Middle East Respiratory Syndrome Coronavirus Infection in South Korea, 2015

Choi, Jun Yong

Between May and July 2015, there was an unexpected outbreak of Middle East respiratory syndrome coronavirus (MERS-CoV) infection in South Korea. The outbreak has emerged as the largest one outside the Middle East. As of July 20, there have been 186 laboratory-confirmed MERS cases, including 36 deaths, 136 recovered individuals discharged from the hospital, and 14 patients who remain in hospitals (Fig. 1) . 1, 2 The index patient was a 68-year-old Korean man. 2 5 The appearance of MERS-CoV was unexpected and unfamiliar to most physicians. Infection prevention and control measures in hospitals were not optimal. Extremely crowded emergency rooms and multi-bed rooms contributed significantly to nosocomial infection in some hospitals. The practice of seeking care at a number of medical facilities may have also been a contributing factor. Additionally, the custom of having many friends and family members accompany or visit patients may have contributed to secondary spread of the infection. Meanwhile, no evidence of community transmission has emerged. Several super-spreading events, which happened within hospitals from patients 1, 14, 16, and 76, contributed to 80% of all subsequent cases. As well, whole genome sequencing of the MERS-CoV from this outbreak did not identify any major mutations different from global MERS-CoV. The factors that drove the super-spreading events of the outbreak have not yet been established. Medical procedures that can generate aerosols from the lower respiratory tract of an undiagnosed patient with severe pneumonia could contribute as a super-spreading event. In addition, the crowdedness of the hospitals and environmental contamination could other reasons for the special event.