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Epidemiol Health. 2018;40(1):e2018014. English. Original Article.
Song YJ , Yang JS , Yoon HJ , Nam HS , Lee SY , Cheong HK , Park WJ , Park SH , Choi BY , Kim SS , Ki M .
Department of Cancer Control and Population Health, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Korea.
Korea National Institute of Health, Korea Centers for Disease Control and Prevention, Cheongju, Korea.
Korean Society of Infectious Diseases, Seoul, Korea.
Department of Preventive Medicine and Public Health, Chungnam National University School of Medicine, Daejeon, Korea.
Department of Preventive Medicine and Public Health, Ajou University School of Medicine, Suwon, Korea.
Department of Social and Preventive Medicine, Sungkyunkwan University School of Medicine, Suwon, Korea.
Department of Preventive Medicine, Hanyang University College of Medicine, Seoul, Korea.


The rates of asymptomatic infection with Middle East Respiratory Syndrome (MERS) coronavirus vary. A serologic study was conducted to determine the asymptomatic MERS infection rate in healthcare workers and non-healthcare workers by exposure status.


Study participants were selected from contacts of MERS patients based on a priority system in 4 regions strongly affected by the 2015 MERS outbreak. A sero-epidemiological survey was performed in 1,610 contacts (average duration from exposure to test, 4.8 months), and the collected sera were tested using an enzyme-linked immunespecific assay (ELISA), immunofluorescence assay (IFA), and plaque reduction neutralization antibody test (PRNT). Among the 1,610 contacts, there were 7 ELISA-positive cases, of which 1 exhibited positive IFA and PRNT results.


The asymptomatic infection rate was 0.060% (95% confidence interval, 0.002 to 0.346). The asymptomatic MERS case was a patient who had been hospitalized with patient zero on the same floor of the hospital at the same time. The case was quarantined at home for 2 weeks after discharge, and had underlying diseases, including hypertension, angina, and degenerative arthritis.


The asymptomatic infection was acquired via healthcare-associated transmission. Thus, it is necessary to extend serologic studies to include inpatient contacts who have no symptoms.

Copyright © 2019. Korean Association of Medical Journal Editors.