BACKGROUND Since the first isolation of Middle East respiratory syndrome coronavirus (MERS-CoV) in Saudi Arabia in 2012, sporadic cases, clusters, and sometimes large outbreaks have been reported. OBJECTIVE To describe the recent (2015) MERS-CoV outbreak at a large tertiary care hospital in Riyadh, Saudi Arabia. METHODS We conducted an epidemiologic outbreak investigation, including case finding and contact tracing and screening. MERS-CoV cases were categorized as suspected, probable, and confirmed. A confirmed case was defined as positive reverse transcription polymerase chain reaction test for MERS-CoV. RESULTS Of the 130 suspected cases, 81 (62%) were confirmed and 49 (38%) were probable. These included 87 patients (67%) and 43 healthcare workers (33%). Older age (mean [SD], 64.4 [18.3] vs 40.1 [11.3] years, P<.001), symptoms (97% vs 58%, P<.001), and comorbidity (99% vs 42%, P<.001) were more common in patients than healthcare workers. Almost all patients (97%) were hospitalized whereas most healthcare workers (72%) were home isolated. Among 96 hospitalized cases, 63 (66%) required intensive care unit management and 60 (63%) required mechanical ventilation. Among all 130 cases, 51 (39%) died; all were patients (51 [59%]) with no deaths among healthcare workers. More than half (54%) of infections were believed to be caught at the emergency department. Strict infection control measures, including isolation and closure of the emergency department, were implemented to interrupt the chain of transmission and end the outbreak. CONCLUSION MERS-CoV remains a major healthcare threat. Early recognition of cases and rapid implementation of infection control measures are necessary. Infect Control Hosp Epidemiol 2016;1-9.

Since the first diagnosis of Middle East respiratory syndrome (MERS) caused by the MERS coronavirus (MERS-CoV) in the Kingdom of Saudi Arabia in 2012, sporadic cases and clusters have occurred throughout the country (1). During June-August, 2015, a large MERS outbreak occurred at King Abulaziz Medical City, a 1,200-bed tertiary-care hospital that includes a 150-bed emergency department that registers 250,000 visits per year.In late June 2015, approximately 3 months after the last previously recognized MERS case in the hospital, a man aged 67 years with multiple comorbidities (diabetes, hypertension, congestive heart failure, and a history of coronary artery bypass graft surgery) and a 10-day history of fever and cough was evaluated in the emergency department ( Figure). The patient had no identified exposure to camels. A nasopharyngeal swab from the patient tested positive for MERS-CoV by reverse transcription-polymerase chain reaction (RT-PCR) (2). The patient was admitted and died in the hospital after 31 days. Although this patient's hospitalization overlapped with the onset of subsequent hospital-associated MERS cases, no direct links between this first case and any of the subsequent cases were identified.Approximately 3 weeks after the first patient's admission, a second patient, a man aged 56 years, with multiple comorbidities (diabetes with hypothyroidism, coronary artery disease, and hypertension with a history of coronary artery bypass surgery) and a history of camel exposure was evaluated in the emergency department for fever, cough, and shortness of breath. His nasopharyngeal specimen tested positive for MERS-CoV by RT-PCR. Three additional cases of MERS were epidemiologically linked to this patient's illness during his first week of hospitalization, including infections in two health care workers from the emergency department. An outbreak investigation was conducted by the hospital's infection control program to identify risk factors for infection and to develop and implement control measures. A suspected MERS case was defined as the occurrence of respiratory symptoms in a person with or without documented exposure to a patient with confirmed or probable MERS infection, but without confirmation by laboratory test results. A probable case was the occurrence of respiratory symptoms in a person with history of exposure to a patient with confirmed or probable MERS infection, but with inconclusive laboratory results (such as positive results by PCR on only one of the two genomic targets). A confirmed case was a suspected or probable case that was subsequently confirmed by a positive RT-PCR test for MERS-CoV. Contacts of persons with confirmed and probable cases were screened and persons with suspected cases were tested.A total of 130 MERS cases were detected at King Abulaziz Medical City during late June-late August. Among these cases, 81 (62%) were confirmed and 49 (38%) were probable, including 43 (33%) cases in health care workers; 20 of these 43 cases (47%) occurred in emergency department health care...

A total 130 cases of Middle East respiratory syndrome coronavirus were identified during a large hospital outbreak in Saudi Arabia; 87 patients and 43 healthcare workers. The majority (80%) of transmission was healthcare-acquired (HAI) infection, with 4 generations of HAI transmission. The emergency department was the main location of exposure.