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

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 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.
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