Clinical and Epidemiologic Characteristics of Spreaders of Middle East Respiratory Syndrome Coronavirus during the 2015 Outbreak in Korea

Abstract

Nosocomial transmission is an important characteristic of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) infection. Risk factors for transmission of MERS-CoV in healthcare settings are not well defined. During the Korean outbreak in 2015, 186 patients had laboratory-confirmed MERS-CoV infection. Those suspected as a source of viral transmission were categorized into the spreader groups (super-spreader [n = 5] and usual-spreader [n = 10]) and compared to the non-spreader group (n = 171). Body temperature of ≥ 38.5°C (adjusted odds ratio [aOR], 5.54; 95% confidence interval [CI], 1.38-22.30; P = 0.016), pulmonary infiltration of ≥ 3 lung zones (aOR, 7.33; 95% CI, 1.93-27.79; P = 0.003), and a more nonisolated in-hospital days (aOR, 1.32 per 1 day; 95% CI, 1.09-1.60; P = 0.004) were significant risk factors in the spreader group. There was no different clinical factor between super-spreaders and usual-spreaders. Nonisolated in-hospital days was the only factor which tended to be higher in super-spreaders than usual-spreaders (Mean, 6.6 vs. 2.9 days; P = 0.061). Early active quarantine might help reducing the size of an outbreak.

Keywords: Hospital Infection; Infection Transmission; Korea; MERS-CoV; Outbreak.

Fig. 1

Epidemiologic characteristics of 2015 Korean MERS-CoV outbreak. (A) Cumulative number of infected patients according to day of illness of each spreader. When infected patients were exposed to a spreader for more than one day, the number of infected patients was equally divided by the duration (day) of exposure. Different colors denote infections transmitted by different spreaders. Note that the 5 super-spreaders transmitted the virus to 92% (161/175) of all cases. (B) Nonisolated in-hospital days according to the date of symptom onset of each patient. Two spreaders transmitted MERS-CoV to healthcare workers despite the fact that they had been isolated before their symptom onset. (C) Days from symptom onset to diagnosis according to the date of symptom onset of each patient. MERS-CoV = Middle East Respiratory Syndrome Coronavirus.

Fig. 2

Contribution of nonisolated in-hospital days to spreading events. (A) Nonisolated in-hospital days in non-spreader, usual-spreader, and super-spreader groups. Dashed lines denote median values at each group. Data points at 0 are shown at different level for clarity. (B) Number of spreaders (S) and infected patients (I), and I/S ratio according to nonisolated in-hospital days of spreaders. There were positive correlation between nonisolated in-hospital days of spreaders and I (red broken line) or I/S ratio (green broken line).