Scope and extent of healthcare-associated Middle East respiratory syndrome coronavirus transmission during two contemporaneous outbreaks in Riyadh, Saudi Arabia, 2017

Abstract

Objective: To investigate a Middle East respiratory syndrome coronavirus (MERS-CoV) outbreak event involving multiple healthcare facilities in Riyadh, Saudi Arabia; to characterize transmission; and to explore infection control implications.

Design: Outbreak investigation.

Setting: Cases presented in 4 healthcare facilities in Riyadh, Saudi Arabia: a tertiary-care hospital, a specialty pulmonary hospital, an outpatient clinic, and an outpatient dialysis unit.

Methods: Contact tracing and testing were performed following reports of cases at 2 hospitals. Laboratory results were confirmed by real-time reverse transcription polymerase chain reaction (rRT-PCR) and/or genome sequencing. We assessed exposures and determined seropositivity among available healthcare personnel (HCP) cases and HCP contacts of cases.

Results: In total, 48 cases were identified, involving patients, HCP, and family members across 2 hospitals, an outpatient clinic, and a dialysis clinic. At each hospital, transmission was linked to a unique index case. Moreover, 4 cases were associated with superspreading events (any interaction where a case patient transmitted to ≥5 subsequent case patients). All 4 of these patients were severely ill, were initially not recognized as MERS-CoV cases, and subsequently died. Genomic sequences clustered separately, suggesting 2 distinct outbreaks. Overall, 4 (24%) of 17 HCP cases and 3 (3%) of 114 HCP contacts of cases were seropositive.

Conclusions: We describe 2 distinct healthcare-associated outbreaks, each initiated by a unique index case and characterized by multiple superspreading events. Delays in recognition and in subsequent implementation of control measures contributed to secondary transmission. Prompt contact tracing, repeated testing, HCP furloughing, and implementation of recommended transmission-based precautions for suspected cases ultimately halted transmission.

Fig. 1

Middle East respiratory syndrome (MERS) cases associated with hospital A (n=38) and hospital B (n=10) outbreaks, Riyadh, Saudi Arabia, from May 28 through June 19, 2017.

Fig. 2

Transmission of MERS-CoV infections between cases at hospital A, an outpatient dialysis unit, and hospital B, Riyadh, Saudi Arabia, from May 28 through June 19, 2017. Cases are shown by date of symptom onset or positive real-time RT-PCR test, except index cases, which are shown by date of hospitalization.

Fig. 3

Real-time reverse-transcription polymerase chain reaction (rRT-PCR) testing results from the date of exposure to the date of first rRT-PCR positive result for healthcare personnel (HCP) cases at hospitals A and B.

Fig. 4

Phylogenetic tree of MERS-CoV genomic sequences from this investigation and previously published sequences within clade 5. White circles indicate cases linked to hospital A, gray circles indicate cases linked to hospital B. All sequences have been deposited in GenBank.