MERS Risk Assessment Highlights High Rate of Hospital Transmissions


The latest World Health Organization report points to high MERS transmission risk in hospitals.

Since Middle East respiratory syndrome-coronavirus (MERS) was first reported in 2012, it has caused cases in 27 countries. A stable source for these outbreaks has been the Kingdom of Saudi Arabia. Because the infection can often be asymptomatic, monitoring trends in outbreaks and educating healthcare workers on isolation precautions is a vital part of infection control. Therefore, an overview of MERS outbreaks, transmission trends, and more, is routinely published by the World Health Organization (WHO).

Since the last WHO MERS report in December 2016, there have been 199 new laboratory-confirmed cases, most of which occurred in Saudi Arabia. The new 2017 report (published in July 2017) highlights several trends within the cases and draws attention to the risks that exist within certain environments. Of the 199 confirmed cases, 58 patients died (29.2%). A total of 72.9% of the patients were male, with a median age of 54 years. Interestingly, 29.6% of the patients were asymptomatic or had mild disease, while 40.2% experienced severe symptoms and / or died.

Although MERS is a zoonotic disease that frequently spills over into humans via infected dromedary camels in the Arabian Peninsula, there have been limited, non-sustained human-to-human transmission in healthcare settings. Hospitals and other healthcare environments have proven to be facilitators in MERS outbreaks, despite significant work to strengthen surveillance, provide early education within the community, and increase compliance with infection prevention and control efforts. The latest WHO report notes that of the cases reported since December 2016, 31% resulted from hospital-associated transmission. A total of 40 of the cases were healthcare workers; however, patients and visitors have also been afflicted. Several outbreaks of MERS in 2017 highlighted the role of hospitals and healthcare workers as vulnerable for transmission.

One such outbreak occurred in Riyadh City, Riyadh where a total of 34 laboratory-confirmed cases of MERS were reported between June 1, 2017 and July 3, 2017. It was determined that the infections originated from a hospitalized man who required emergency medical care. During the outbreak investigation, it was found that prior to the patient’s diagnosis, 220 healthcare workers, patients, and visitors were exposed to the virus.

The report also highlights other cases of MERS outbreaks associated with healthcare-setting exposure, which impacted laboratory workers, emergency medical staff, nurses, and other healthcare workers. To this end, the WHO report highlights the challenges of identifying the drivers for healthcare transmission, and how the role of asymptomatic cases (and contact) is a likely contributory component. Indeed, many clusters originate from transmission that most likely occurred prior to the initiation of infection prevention and control procedures, especially when performing tasks such as aerosol-generating procedures in busy emergency departments or patient rooms, without the proper infection control measures.

The WHO risk assessment within this report points to the frequent presence of healthcare transmission and the fact that the non-specific symptoms often seen with MERS can be challenging for surveillance and isolation adherence. As such, WHO has implemented ongoing investigations to better understand the transmission mechanisms within the healthcare setting and the role certain exposures play in transmission.

Interestingly, WHO updated its surveillance guidance for MERS to require that healthcare facilities screen individuals presenting with respiratory symptoms (who also recently visited the Middle East for recent hospitalization or to visit another healthcare facility) and if they had contact (direct or indirect) with dromedary camels. Prior to this requirement, travel was the most important screening tool; however, the inclusion of visits to a healthcare facility within the screening algorithm is especially fascinating.

While researchers work to better understand the spread of MERS and how healthcare facilities act as facilitators, it is important to encourage basic infection prevention practices, such as having patients with a cough wear a mask during the screening/triage process, utilizing appropriate hand hygiene, etc. While we work to better understand MERS transmission, strengthening infection prevention and control practices can only help stop the spread of disease.

Three clinical trials are currently underway to evaluate the antiviral treatment of MERS: a convalescent therapy treatment trial at stage 2 set to complete in June 2017 (, NCT02190799), an anti-spike protein antibody safety and pharmacokinetics study set to complete in April 2018 (, NCT02788188), and a lopinavir/ritonavir and interferon beta1b trial that is still recruiting (, NCT02845843). WHO is not involved in these clinical trials.

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