Nosocomial outbreak of the Middle East Respiratory Syndrome coronavirus: A phylogenetic, epidemiological, clinical and infection control analysis

Abstract Background Middle East Respiratory Syndrome coronavirus (MERS-CoV) continues to cause intermittent community and nosocomial outbreaks. Obtaining data on specific source(s) and transmission dynamics of MERS-CoV during nosocomial outbreaks has been challenging. We performed a clinical, epidemiological and phylogenetic investigation of an outbreak of MERS-CoV at a University Hospital in Riyadh, Kingdom of Saudi Arabia. Methods Clinical, epidemiological and infection control data were obtained from patients and Healthcare workers (HCWs). Full genome sequencing was conducted on nucleic acid extracted directly from MERS-CoV PCR-confirmed clinical samples and phylogenetic analysis performed. Phylogenetic analysis combined with published MERS-CoV genomes was performed. HCWs compliance with infection control practices was also assessed. Results Of 235 persons investigated, there were 23 laboratory confirmed MERS cases, 10 were inpatients and 13 HCWs. Eight of 10 MERS inpatients died (80% mortality). There were no deaths among HCWs. The primary index case assumed from epidemiological investigation was not substantiated phylogenetically. 17/18 of MERS cases were linked both phylogenetically and epidemiologically. One asymptomatic HCW yielded a MERS-CoV genome not directly linked to any other case in the investigation. Five HCWs with mild symptoms yielded >75% full MERS-CoV genome sequences. HCW compliance with use of gowns was 62.1%, gloves 69.7%, and masks 57.6%. Conclusions Several factors and sources, including a HCW MERS-CoV ‘carrier phenomenon’, occur during nosocomial MERS-CoV outbreaks. Phylogenetic analyses of MERS-CoV linked to clinical and epidemiological information is essential for outbreak investigation. The specific role of apparently healthy HCWs in causing nosocomial outbreaks requires further definition.