title: MERS-CoV outbreak following a single patient exposure in an emergency room in South Korea: an epidemiological outbreak study.
abstract: BACKGROUND
  In 2015, a large outbreak of Middle East respiratory syndrome coronavirus (MERS-CoV) infection occurred following a single patient exposure in an emergency room at the Samsung Medical Center, a tertiary-care hospital in Seoul, South Korea. We aimed to investigate the epidemiology of MERS-CoV outbreak in our hospital.
  
  
  METHODS
  We identified all patients and health-care workers who had been in the emergency room with the index case between May 27 and May 29, 2015. Patients were categorised on the basis of their exposure in the emergency room: in the same zone as the index case (group A), in different zones except for overlap at the registration area or the radiology suite (group B), and in different zones (group C). We documented cases of MERS-CoV infection, confirmed by real-time PCR testing of sputum samples. We analysed attack rates, incubation periods of the virus, and risk factors for transmission.
  
  
  RESULTS
  675 patients and 218 health-care workers were identified as contacts. MERS-CoV infection was confirmed in 82 individuals (33 patients, eight health-care workers, and 41 visitors). The attack rate was highest in group A (20% [23/117] vs 5% [3/58] in group B vs 1% [4/500] in group C; p<0·0001), and was 2% (5/218) in health-care workers. After excluding nine cases (because of inability to determine the date of symptom onset in six cases and lack of data from three visitors), the median incubation period was 7 days (range 2-17, IQR 5-10). The median incubation period was significantly shorter in group A than in group C (5 days [IQR 4-8] vs 11 days [6-12]; p<0·0001). There were no confirmed cases in patients and visitors who visited the emergency room on May 29 and who were exposed only to potentially contaminated environment without direct contact with the index case. The main risk factor for transmission of MERS-CoV was the location of exposure.
  
  
  CONCLUSIONS
  Our results showed increased transmission potential of MERS-CoV from a single patient in an overcrowded emergency room and provide compelling evidence that health-care facilities worldwide need to be prepared for emerging infectious diseases.
  
  
  BACKGROUND
  None.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Cho
authors.affiliation: Division of Infectious Diseases, Department of Paediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Ji-Man
authors.initials: JM
authors.lastname: Kang
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Young Eun
authors.initials: YE
authors.lastname: Ha
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Ga Eun
authors.initials: GE
authors.lastname: Park
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Ji Yeon
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Ko
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Ji Yong
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Division of Infectious Diseases, Department of Paediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Kim
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Cheol-In
authors.initials: CI
authors.lastname: Kang
authors.affiliation: Department of Emergency Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Ik Joon
authors.initials: IJ
authors.lastname: Jo
authors.affiliation: Infection Control Office, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Jae Geum
authors.initials: JG
authors.lastname: Ryu
authors.affiliation: Infection Control Office, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Jong Rim
authors.initials: JR
authors.lastname: Choi
authors.affiliation: Biostatistics team, Samsung Biomedical Research Institute, Seoul, South Korea.
authors.forename: Seonwoo
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Hee Jae
authors.initials: HJ
authors.lastname: Huh
authors.affiliation: Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Chang-Seok
authors.initials: CS
authors.lastname: Ki
authors.affiliation: Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Eun-Suk
authors.initials: ES
authors.lastname: Kang
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Kyong Ran
authors.initials: KR
authors.lastname: Peck
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Hun-Jong
authors.initials: HJ
authors.lastname: Dhong
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Song
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea. Electronic address: iddrchung@gmail.com.
authors.forename: Doo Ryeon
authors.initials: DR
authors.lastname: Chung
authors.affiliation: Division of Infectious Diseases, Department of Paediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea. Electronic address: yaejeankim@skku.edu.
authors.forename: Yae-Jean
authors.initials: YJ
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018352:Coronavirus Infections / Q000175:diagnosis / Q000453:epidemiology / Q000635:transmission*; D003428:Cross Infection / Q000517:prevention & control / Q000635:transmission; D003441:Crowding; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D018562:Disease Transmission, Infectious; D004636:Emergency Service, Hospital; D005260:Female; D006282:Health Personnel / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D065207:Middle East Respiratory Syndrome Coronavirus / Q000302:isolation & purification*; D016273:Occupational Exposure / Q000706:statistics & numerical data; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D055815:Young Adult