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Critical Illness and MERS

Amesh A. Adalja, MD, FACP, FACEP, FIDSA, September 29, 2017

Cases of Middle East respiratory syndrome (MERS) have continued to accrue in the Arabian Peninsula over the past several years and have been imported to other nations, most notably South Korea. While some cases of MERS are minimally symptomatic, such as the 2 cases imported into the United States, some are characterized by severe symptoms and death. A new retrospective multicenter cohort study, published in Critical Care Medicine, focused on critically ill MERS patients in Saudi Arabia and provides important information on the characteristics of those with the most severe manifestations.


Independent Risk Factor for Death

In this study, Arabi et al. included 330 patients from 14 referral centers in Saudi Arabia who were diagnosed with severe acute respiratory infection due to MERS and compared them to 222 who had severe acute respiratory infection due to a non-MERS etiology. The study period included patients admitted between September 2012 and October 2015.

Important differences between patient cohorts included the fact that they tended to be younger, male, and healthcare workers. Clinically, they tended to be more hypoxemic with more extensive chest radiographic findings than non-MERS patients. SOFA scores were also higher. Accordingly, they were more likely to require mechanical ventilation and higher oxygen concentrations and positive end expiratory pressure. They were also more likely to receive paralytics, nitric oxide, prone position ventilation, high-frequency oscillatory ventilation, and extracorporeal membrane oxygenation (ECMO). Vasopressor use and renal replacement therapy were used more frequently in MERS patients. 

MERS survivors tended to clear the virus faster than MERS nonsurvivors. Viral coinfections were present in 5% of MERS patients--most commonly, another coronavirus, RSV, and influenza A. Bacteremia was present in 8% of MERS patients.

Mortality was 65.8% in the MERS group compared to 31.1% in the non-MERS group, and MERS was an independent risk factor for death. In MERS patients, age and renal failure were associated with death. Death from community-acquired MERS was associated with age and diabetes with complications. 



This study, the largest ever on MERS patients, is an important addition to the literature on this highly significant emerging infectious disease. The severity described with MERS, when compared to patients with similar clinical syndromes not caused by MERS, is substantial and illustrates the challenges in treating severe cases of MERS. Importantly, rescue therapies such as ECMO were employed more frequently with MERS patients, and this use will be important to study in detail for evidence of benefit and feasibility of regionalization as well as application to other severe respiratory infections.

As MERS continues to spill into humans, clinical and epidemiologic data will be essential for preparedness activities, situational awareness, and resilience.



Arabi YM, Al-Omari A, Yasser M, et al. Critically ill patients with the Middle East respiratory syndrome: a multicenter retrospective cohort study. Crit Care Med 2017;45(10):1683-1695.