Infection Control & Hospital Epidemiology
Transmission from patient cases to HCP participating in aerosolizing procedures prior to airborne precautions was likely, despite taking recommended airborne precautions and wearing appropriate PPE. MERS-CoV has been detected in large quan- tities in respiratory secretions25 and live virus isolated from environmental surfaces.7 It is possible that inappropriate use of PPE (eg, insufficient fit testing) or contamination of PPE and inappropriate doffing resulted in transmission. Transmission to HCP wearing isolation gowns and N95 respirators during intu- bation has been observed previously.26,27 HCP should ensure appropriate fit testing and donning and doffing of PPE to prevent MERS-CoV transmission. Among the 17 HCP cases tested by serology, 11 (65%) had no
detectable antibodies. The 4 seropositive HCP cases (24%) each had either evidence of pneumonia or symptoms suggestive of lower respiratory tract infection, consistent with previous evi- dence that HCP cases with lower-respiratory-tract symptoms are more likely to have detectable antibodies.28 The use of serologic testing to detect unrecognized infections in asymptomatic or mildly symptomatic individuals may be limited.29 In both outbreaks, rapid identification of contacts, symptom
monitoring, and repeated testing allowed for efficient detection of secondary HCP cases and provided information to guide outbreak management. Of the 25 HCP-cases, 10 were detected on initial rRT-PCR testing and 15 by repeated rRT-PCR testing, including multiple HCP cases who initially tested rRT-PCR– negative up to 7 days after known case exposure, indicating that asymptomatic or mildly symptomatic HCP may require repe- ated screening to rule out infection. Although we found no evidence of transmission from HCP to HCP, rapid furlough of MERS-CoV positive HCP is important to avoid exposing sus- ceptible individuals, particularly patients, to MERS-CoV positive HCP. Our investigation had several limitations. Complete medical
records were not available for all patients. Seropositivity may have been a result of unknown exposures outside of this outbreak. Although hospitalized patients have been shown to develop MERS-CoV antibody responses after 3 weeks,30 MERS-CoV antibody kinetics over time are not fully understood, particularly in asymptomatic or mildly ill individuals. Genome sequencing was limited by sample quality, and full-genome sequences were not available from all patient samples. HCP PPE use was assessed via interview, so errors in recollection may have been incorpo- rated into our data. Due to the retrospective nature of this investigation, IPC practices during potential transmission events could not be confirmed by observation. The introduction of MERS-CoV into healthcare facilities
continues to occur, resulting in substantial morbidity and mor- tality. In these 2 contemporaneous but epidemiologically unre- lated outbreaks, superspreading events were associated with extensive transmission and disruptions to hospital operations, including large-scale furloughing of exposed HCP. Early recog- nition of cases, rapid implementation of recommended IPC measures, and aggressive contact tracing and repeated testing are necessary to effectively prevent and interrupt transmission of MERS-CoV. (Fig. 4)
Acknowledgments. The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the US Centers for Disease Control and Prevention.
Financial support. No financial support was provided relevant to this article.
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Conflicts of interest. All authors report no conflicts of interest relevant to this article.
Supplementary Material. To view supplementary material for this article, please visit
https://doi.org/10.1017/ice.2018.290
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