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‘Super-spreader’ patient infected 82 with MERS at South Korea hospital
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A new study shows how one patient with Middle East respiratory syndrome, or MERS, infected 82 other individuals in one hospital during last year’s MERS outbreak in South Korea.
MERS, first reported in humans in 2012, is caused by a coronavirus (MERS-CoV) and has mostly been diagnosed in Saudi Arabia, where the bulk of the more than 1,700 cases have occurred. No country outside of Saudi Arabia, however, has seen more cases than South Korea, where 186 people were infected during 2 months in 2015. Thirty-six of those patients died.
Researchers who analyzed the so-called “super-spreader” patient’s impact on Samsung Medical Center in Seoul said overcrowding in the ED played a role in the nosocomial outbreak.
The patient was responsible for 44% of the country’s total number of MERS infections during the outbreak.
“The potential for similar outbreaks anywhere in the world from a single traveler should be noted, as long as MERS-CoV transmission continues in the Middle East,” they wrote in The Lancet. “Emergency preparedness and vigilance are crucial to the prevention of further large outbreaks in the future.”
Man was infected by South Korea’s first MERS patient
Researchers conducted a retrospective investigation of the outbreak at the medical center that included a review of closed-circuit security video footage and electronic medical records.
Before arriving at the hospital in late May, the super-spreader patient — a man aged 35 years — was exposed to MERS at another facility by South Korea’s first-ever MERS patient, a man aged 68 years who was likely infected while traveling in the Middle East.
Although both patients wound up at Samsung, only the super-spreader patient transmitted the virus there.
Indeed, the researchers found that while the index patient had infected 28 individuals at other health care facilities, he did not infect anyone at Samsung despite coming in contact with 478 patients and health care workers. In contrast, the super-spreader patient came in contact with 1,576 people over 3 days after being admitted to the Samsung ED, which sees more than 200 patients per day.
He was admitted on May 27 and was only isolated on May 29 after the hospital received notice that he may have been exposed to the index patient. In that time, he infected 33 other patients, 41 visitors and eight health care workers.
Those exposed to the virus were classified into groups based on their proximity to the man in the ED. Researchers found that the main risk for transmission of MERS-CoV was the location of exposure: The attack rate for those who were in the same zone as him was 20% — highest among three groups. Among individuals who were in a different zone but contacted the patient at registration or in the radiology suite, the attack rate was 5%. It was 1% in individuals who remained in a different zone.
The median incubation period was 7 days for all cases, but was much shorter in the first group compared with the third group: 5 days vs. 11 days. Further, there were no reported cases of infections in patients or visitors who were only exposed to a potentially contaminated environment after the man was isolated on May 29.
“To our knowledge, we are the first to document group-specific incubation periods and attack rates,” the researchers wrote. “Our results showed the increased transmission potential of MERS-CoV from a single patient in an overcrowded emergency room setting. Overcrowding is an important issue for this outbreak and is also a common feature of modern medicine.”
Isolation failures evident in report
In a related commentary, David S. Hui, MD, professor of medicine and therapeutics in the Stanley Ho Center for Emerging Diseases at the Chinese University of Hong Kong, said other factors contributed to the outbreak at Samsung Medical Center.
These factors, Hui wrote, included “failure to implement strict isolation of patients and quarantine of contacts at the first outbreak hospital (Pyeongtaek St Mary’s Hospital), poor communication and knowledge of patient movement between hospitals, overcrowding in the emergency room, inadequate ventilation with only three air changes per [hour], and limited availability of isolation rooms in the emergency room.”
Hui noted that infection control failures have led to large numbers of secondary MERS cases at hospitals in Saudi Arabia and other countries.
“Common risk factors include exposure to contaminated and overcrowded health care facilities, poor compliance with appropriate personal protection equipment when assessing patients with febrile respiratory illness, application of potential aerosol-generating procedures (eg, resuscitation, continuous positive airway pressure, nebulized drugs), and lack of proper isolation room facilities,” he wrote. – by Gerard Gallagher
Disclosure: The researchers report no relevant financial disclosures. Hui reports being a member of the joint WHO-Republic of Korea Urgent Mission for the investigation of South Korea’s MERS outbreak.
Perspective
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William Schaffner
The study describes every infection controller’s nightmare: a patient who is highly infectious (a super-spreader) with a life-threatening respiratory infection comes into your crowded ED, is not recognized as a hazard, is not put in isolation, thus exposing 675 patients, 218 health care workers and an estimated 683 visitors. After the dust of the investigation had settled, MERS-CoV infection was confirmed in 33 patients, eight health care workers and 41 visitors. There are several lessons here, including the critical importance of a travel history. It is ancient and the lowest tech, but still powerful. Unde venis? Where have you been? Today, with our ever-smaller world, the need to ask this simple question of everyone who presents with a respiratory illness is critical. We have had several candidate MERS-CoV patients come to our ED; they have been identified at their initial presentation and were promptly placed in isolation. The infection control team was notified STAT; appropriate specimens were obtained; colleagues at the state health department notified, and results were returned within a brief period. Things worked as the textbook said it should, but only because a great deal of preparation and training had gone on before. Back in the day, making sure that the question was asked was a potential weak link. Today, however, the EMR is the infections controller’s friend because the travel-related questions are programmed into the initial ED encounter; the questions are right at the top and, if not answered, the interview cannot proceed.
With Zika, Ebola, MERS-CoV, dengue, chikungunya, novel influenza, measles and other pathogens hovering just beyond our borders, any of them could be at our doorsteps at any time. It’s a small world — where have you been?
Disclosure: Schaffner reports no relevant financial disclosures.
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