Though Zika has eclipsed it as a national concern, another virus that has already caused many occupational infections and even deaths in healthcare workers is still emerging in hospital outbreaks a plane ride away: Middle East Respiratory Syndrome (MERS).

The World Health Organization recently reported an outbreak of the MERS coronavirus in a hospital in Riyadh, Saudi Arabia, where a single patient infected 24 contacts — 11 of them healthcare workers.1 Similarly, researchers recently documented the explosive spread of MERS last year from a single patient in a Korean ED to eight healthcare workers and scores of patients.2

These transmissions to numerous contacts from a single infected case reopened discussions of “super-spreaders,” a phenomenon also observed in the 2003 outbreak of a similar coronavirus, Severe Acute Respiratory Syndrome (SARS). (See related story in this issue.)

Still, there may be some sense of complacency in the U.S., as MERS was contained in 2014 when two unrelated cases were admitted to hospitals in Indiana and Florida. Those cases involved healthcare workers who had recently worked in Saudi Arabian hospitals, but next time MERS may not be so obviously identified. Crowded U.S. EDs could certainly be vulnerable to an undiagnosed MERS patient, thus a familiar colloquialism applies to the situation.

“It’s true it ain’t over till it’s over — and MERS ain’t over yet,” says William Schaffner, MD, an epidemiologist in the department of preventive medicine at Vanderbilt University Medical Center in Nashville, TN. “We can all use a reminder that it is not over and to stay alert.”

Camels in Saudi Arabia are the likely reservoir host for the virus, which appears to be originally of bat origin. MERS does not spread effectively in the community, but can cause hospital outbreaks that often include transmission to healthcare workers.

“There is no question that primary cases are continuing to occur at a steady rate,” says Allison McGeer, MD, a microbiologist and infectious disease consultant at Mount Sinai Hospital in Toronto. “I think there are far fewer secondary cases and that there are presumably fewer exported cases. There is still a risk of travel-associated cases and there is no evidence that that risk is going to go away. All of us around the world are still at risk of a travel-associated case triggering an outbreak.”

640 MERS Deaths

As of July 30, 2016, WHO reported that MERS has caused 1,791 confirmed infections and 640 deaths since first emerging in Saudi Arabia in September 2012. It is still largely confined to the kingdom, though 27 countries have reported cases via travelers from the region. The overall case count translates to a mortality rate of 35%, with deaths occurring primarily in those with underlying medical conditions. Hospital Employee Health asked for more information on the number of infections and subsequent outcomes in healthcare workers, but neither WHO nor the CDC provided information as this issue went to press.

However, it is widely known that many healthcare workers have been infected with MERS in hospital outbreaks. Without citing a specific number, a recently published paper confirms fatal MERS infections have occurred among healthcare workers. In addition, the researchers cited the emotional toll on workers of seeing colleagues become very sick and end up hospitalized alongside patients during the outbreak. (See related story in this issue.)

MERS has caused severe infections and deaths in healthcare workers, says McGeer, who was on the frontlines of the SARS outbreak in Toronto that resulted in 400 infections and 41 deaths in patients and three healthcare workers. The SARS outbreak that began in China spread globally, eventually causing more than 8,000 infections and some 775 deaths. It is estimated that about 20% of the total SARS cases were healthcare workers. In a point particularly germane to the current situation with MERS, the Toronto outbreak began with a case of unrecognized SARS in an infected contact of a recent traveler to the Hong Kong epicenter.

“There are healthcare workers who have died of MERS, but the majority of healthcare workers’ cases are either asymptomatic or minimally symptomatic” McGeer says. “The majority of healthcare workers with SARS had symptoms and the case fatality rate was higher.”

In the Saudi hospital outbreak reported recently by WHO, most of the infected healthcare workers were, indeed, asymptomatic or had mild symptoms and were confined to home isolation. However, one serious case developed in a 28-year-old male healthcare worker who was exposed to the index case, developed symptoms, and was admitted to the hospital. The worker, who has no comorbidities, was in stable condition after being admitted to a negative pressure isolation room, WHO reported.

A WHO report on June 22, 2016, stated the index patient was admitted to a Saudi hospital in critical condition with MERS undiagnosed because it was “masked by other predominant symptoms.” She was admitted through the ED and began showing signs of respiratory illness before death. MERS symptoms commonly include fever, cough, and shortness of breath. Pneumonia develops in many cases, and gastrointestinal symptoms like diarrhea have also been reported.

“Following admission the patient showed signs of respiratory illness and MERS was suspected,” the WHO states. “The hospital diagnosed and confirmed MERS on June 12, 2016, within 48 hours of her original admission.”

A 14-hour Flight

Thus, a single undiagnosed case infected 11 healthcare workers and 13 other patients, visitors, and contacts in a country with a high suspicion for cases and experience with MERS outbreaks. That may not bode well for future introductions of a MERS case in a U.S. hospital — for example, one in Washington, DC, that is a 14-hour nonstop flight from Riyadh.

“I think even with a really good healthcare system, you will miss an index case and then detect a case as part of a nosocomial outbreak,” McGeer says. “Twenty-five years ago, detecting dengue in my hospital was not an issue, but now it is. Detecting things like MERS has been helpful, because travel history is not just something needed in terms of infection control — it is helpful in terms of individual-level diagnosis [and treatment].”

Complicating the situation, a study published last year raised the possibility of transmission from those with asymptomatic MERS. There appear to be thousands of asymptomatic or mild MERS cases — primarily young men who have frequent contact with camels — who may be transmitting the virus to those with underlying medical conditions in Saudi Arabia, according to a seroprevalence study.3 That said, U.S. hospitals may have to run that risk as long as they can at least pick up incoming symptomatic MERS cases.

“In North America you just have to pick up the travelers to get the people at risk, but in Saudi Arabia you have to treat everybody who might have a respiratory infection as if they had a MERS infection — that it is a huge burden,” says McGeer, who has traveled to the kingdom to investigate the hospital outbreaks. “From my perspective, it has been really hard for Saudi Arabia to get this far, but the good news in this latest outbreak is that less than a week from what appeared to be the index case, there was a report to WHO [disclosing that a case was missed and transmission occurred]. That’s as good as it is going to get in Saudi Arabia. They are going to miss cases.”

Though no transmission has occurred in the U.S., the 2014 MERS introductions caused considerable chaos and concern. The CDC initially reported that an Indiana man with MERS transmitted it via handshake to a man from Illinois, but more refined testing revealed the suspected secondary case did not have the coronavirus. None of the American healthcare workers exposed to the first two MERS cases were infected, but all were subject to rapid follow-up and home quarantine policies following the exposures. For example, in the hours before MERS was suspected in the second U.S. case in Orlando, several employees in a hospital ED had unprotected exposures. Two physicians and 14 other healthcare workers at Dr. P. Phillips Hospital were placed on home isolation for the 14-day MERS incubation period. Another seven healthcare workers at Orlando Regional Medical Center were furloughed after it was discovered they were exposed when the patient accompanied a friend to the radiology department there.

MERS Vigilance

The U.S. introductions certainly raised MERS awareness, as hospitals like Vanderbilt follow-up rapidly when they identify a suspect case, Schaffner says. The travel piece is critical because the initial onset of MERS can be virtually indistinguishable from other severe respiratory infections.

“We have not had any MERS, but we have had several ‘alerts’ on patients who have been evaluated as possible MERS introductions,” he says. “That system has worked very well. The patient immediately gets put into isolation, infection control is notified, and they are on the scene. Specimens are obtained and the state health department laboratory is notified and the specimens are sent to the state lab and are managed with appropriate security. We get answers pretty darn quick.”

Likewise, McGeer sees about one case a month of a patient with severe respiratory symptoms and a travel or contact history that would raise the possibility of MERS infections.

“The screening question in our emergency department is, ‘Have you or any of your close contacts traveled?’” she says. “That testing gets done in six hours and the second that testing result is available, every hospital in the province will know what’s going on in my hospital. I would say we send testing for MERS once a month.”

Of course, many healthcare workers and patients may already be exposed by the time a MERS case is diagnosed. Even if precautions are indicated, surveillance data and exposure reports are a cause for concern. For example, the International Safety Center’s Exposure Prevention Information Network (EPINet) 2012-2014 occupational incident surveillance data indicates that, during a mucotaneous blood or body fluid exposure, healthcare workers are only wearing face-appropriate barrier protection or PPE (mask, respirator, eye protection, face shield) 14% of the time.

“This leaves a gaping window of risk open for occupationally acquired respiratory threats,” says Amber Mitchell, PhD, center director. “It creates an environment where the risk of transmission of occupational illness is extremely high, especially with MERS, which continues to be a public health threat in the Middle East and Asia. As the WHO indicates, it is not always possible to identify patients with MERS early, meaning that being diligent about access to and use of appropriate PPE and barrier garments becomes increasingly important to protect healthcare providers.”

Preventing Exposures

To prevent these exposures from the outset, the CDC recommends respiratory “etiquette” signs and posters reminding patients and healthcare workers to adhere to respiratory hygiene and cover coughs while practicing hand disinfection and following triage procedures.4

“Instructions should include how to use facemasks or tissues to cover nose and mouth when coughing or sneezing, to dispose of tissues and contaminated items in waste receptacles, and how and when to perform hand hygiene,” CDC recommends. “Implement respiratory hygiene and cough etiquette (i.e., placing a facemask over the patient’s nose and mouth) and isolate those at risk for MERS-CoV infection in an airborne infection isolation room.”

It is striking that MERS has emerged in the Middle East but has not been able to really establish an endemic foothold in another region in the absence of its camel reservoir. That said, as we have seen with Zika virus, the longer the MERS coronavirus is loose in the world and causing infections, the greater the likelihood that it could eventually mutate to become more transmissible between humans.

“Each of these infections — SARS, Ebola, Zika and MERS — are distinctive and there are still unknowns about all of them,” Schaffner says. “The appearance of widespread SARS in Canada but not in the U.S. and not in Europe — and then the sudden disappearance of SARS — still has most of us perplexed. The epidemiology and reservoir of MERS in the Middle East has been somewhat elucidated but it is still, to some extent, a mystery. There are people infected who have no contact with camels and there is no big epidemic of MERS in the camel herders and owners, so what is going on there? It’s really very puzzling to us.”


  1. WHO. Update and clarification on recent MERS cases reported by the Kingdom of Saudi Arabia. Geneva, Switzerland. 23 June 2016:
  2. Sun YC, Kang JM, Young EH, et al. MERS-CoV outbreak following a single patient exposure in an emergency room in South Korea: an epidemiological outbreak study. Lancet. Published online July 8, 2016:
  3. Muller MA, Meyer B, Corman VM, et al. Presence of Middle East respiratory syndrome coronavirus antibodies in Saudi Arabia: A nationwide, cross-sectional, serological study. Lancet Infect Dis 2015; 15 (5)559–564.
  4. CDC. Interim Infection Prevention and Control Recommendations for Hospitalized Patients with Middle East Respiratory Syndrome Coronavirus (MERS-CoV):