r e s e a r c h b r i e f s Seroprevalence of Middle East Respiratory Syndrome Coronavirus Among Healthcare Personnel Caring for Patients With Middle East Respiratory Syndrome in South Korea The outbreak of Middle East respiratory syndrome coronavirus (MERS-CoV) in South Korea resulted in 186 infections and 36 deaths in 2015. One of the characteristics of the outbreak is that nearly all transmissions occurred in the hospitals and 39 (21.0%) of 186 confirmed cases were healthcare personnel (HCP).1 National Medical Center (NMC) is a 450-bed teaching hospital acting as a hub of nationwide public healthcare institutions and a total of 30 of 186 confirmed MERS-CoV patients were admitted to the NMC during the MERS-CoV outbreak from May to July in 2015. All cases were referred after the confirmation of MERS-CoV infection and were admitted to negative pressure isolation rooms. The level of personal protective equipment for HCP was determined on the basis of the expected level of contact with patients. In general, HCP wore gloves, a fluid-resistant coverall, either protective glasses or a face shield, and an N95 respirator. During aerosol- generating procedures or when caring for patients under mechanical ventilator care, HCP wore inner and outer gloves, an impermeable coverall, a powered air-purifying respirator with external belt-mounted blower, full face shield (hood), inner and outer boot covers, and an apron. During the MERS-CoV patient care period, 4 accidental exposure events among HCP were reported to the hospital authority (Table 1). Case 1 reported exposure to the blood of a patient on bare skin. Although there was no visible breakage in the exposed skin area, he was quarantined because the exposed skin area was as large as 25 cm2. Case 2 reentered the isolation room while she was doffing in the anteroom and contacted the MERS patient for approximately 5 minutes without adequate respirator protection. Case 3 accidentally entered the isolation room with a disconnected circuit of the powered air-purifying respirator for approximately 10 minutes. Case 4 experienced disconnection of the circuit of the powered air-purifying respirator during the endotracheal intubation procedure and exposure time was estimated as approximately 30 seconds. The patients to whom cases 1 and 4 were exposed presented active pneumonia with sputum positive for MERS by reverse transcription–polymerase chain reaction at the time of exposure. No data are available to determine whether the patient was viremic in case 1 (whose skin was exposed to the blood of a patient). In the other cases, pneumonia was improving and the results of sputum testing for MERS by reverse transcription–polymerase chain reaction were equivocal or negative at the moment of exposure. All of the involved HCP were quarantined for 14 days and none of them developed MERS-like symptoms. To capture any subclinical infections, serosurvey was performed after the outbreak termination. Among the 333 HCPs who had participated in care of MERS patients, 285 consented to participate in the study and none revealed reactive result for MERS-CoV S1 immunoglobulin G enzyme- linked immunosorbent assay (Euroimmun) whereas 109 HCP (38.2%) reported that they experienced MERS-like symptoms during the period of care of MERS patients. HCP are one of the high-risk populations for MERS-CoV infection2,3 and inadequate infection control measures have been reported to be responsible for the in-hospital acquisition of MERS.3,4 Whereas symptomatic HCP were related with in-hospital superspreading events during the severe acute respiratory syndrome outbreak,5 a study conducted in Saudi Arabia reported that the attack rate of MERS-like symptoms was lower among the HCP who were exposed to a MERS-CoV case-patient than among the HCP without exposure (22% vs 33%) and none of them showed evidence of MERS-CoV infection.6 In line with that finding, only 19 (1.1%) among 1,695 HCP contacts of confirmed MERS cases tested positive in Saudi Arabia, which indicated a rather small risk of transmission to HCP.4 However, apparent heterogeneity exists leading to sporadic outbreaks7 and NMC adopted a higher infection precaution level than generally recommended, especially during aerosol-generating procedures or when caring for patients under mechanical ventilator care. Actually, 7 HCP contracted MERS at a different single institution table 1. Accidental Exposure Cases During Care of Patients With MERS Case no. Occupation Sex Age, y PPE Mode of exposure 1 Doctor Male 42 N95 Contact with patient’s blood on bare skin 2 Nurse Female 52 None Exposure to sick patient under MV without PPE for 5 min 3 Doctor Male 40 PAPR PAPR circuit disconnect for 10 min 4 Doctor Male 38 PAPR PAPR circuit disconnect for 30 sec NOTE. MERS, Middle East respiratory syndrome; MV, mechanical ventilation; PAPR, powered air-purifying respirator; PPE, personal protective equipment. infection control & hospital epidemiology december 2016, vol. 37, no. 12 http://dx.doi.org/10.1017/ice.2016.221 Downloaded from http:/www.cambridge.org/core. University of Toronto, on 01 Jan 2017 at 23:20:20, subject to the Cambridge Core terms of use, available at http:/www.cambridge.org/core/terms. in South Korea during the care of patients with known status of MERS infection8 whereas there was no seroconversion case among the 443 HCP with adequate personal protective equipment during the 2015 MERS outbreak in South Korea.9 In summary, there was no evidence of MERS-CoV infection among the HCP who participated in the care of 30 patients in NMC although a substantial proportion of HCP reported that they experienced MERS-like symptoms during the patient care period. Our results suggest that risk of MERS acquisition among HCP is low under stringent infection control measures. acknowledgments We thank Yu Mi Jung for technical assistance in data analysis, and we appreciate Professor Sara Gianella for her stimulating advice during the manuscript preparation. Financial support. NMC Research Institute (grant NMC2015-MS-03). Potential conflicts of interest. All authors report no conflicts of interest relevant to this article. Ji Yeon Lee, MD;1 Gayeon Kim, MD;2 Dong-Gyun Lim, MD;3 Hyeon-Gun Jee, PhD;3 Yunyoung Jang, RN;4 Joon-Sung Joh, MD;1 Ina Jeong, MD;1 Yeonjae Kim, MD;2 Eunhee Kim, RN;4 Bum Sik Chin, MD, PhD2 Affiliations: 1. Division of Pulmonary and Critical Care Medicine, Depart- ment of Internal Medicine, National Medical Center, Seoul, Republic of Korea; 2. Center for Infectious Diseases, National Medical Center, Seoul, Republic of Korea; 3. Center for Chronic Diseases, Research Institute, National Medical Center, Seoul, Republic of Korea; 4. Infection Control Unit, National Medical Center, Seoul, Republic of Korea. Address correspondence to Bum Sik Chin, MD, PhD, Center for Infectious Diseases, National Medical Center, 245, Euljiro, Jung-gu, Seoul 100-799, Republic of Korea (