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The rapid transmission and high attack rate of MERS-CoV in a hospital dialysis unit in Al-Hufuf, Saudi Arabia “raises substantial concerns about the risk of health care–associated transmission of this virus,” a team of researchers reported recently in the New England Journal of Medicine.
A team that included Allison McGeer, MD -- a microbiologist and infectious disease consultant at Mount Sinai Hospital in Toronto who battled the SARS outbreak in 2003 – reviewed an outbreak of MERS-CoV that occurred between April 1 and May 23, 2013. A total of 23 confirmed cases and 11 probable cases were part of a single outbreak involving four health care facilities in Saudi Arabia.
“The apparent heterogeneity in transmission, with many infected patients not transmitting disease at all and one patient transmitting disease to seven others, is reminiscent of SARS,” the team reported.
This so called “super spreader” phenomenon was further evidenced by a patient that transmitted the novel virus to three people and four patients who transmitted infection to two persons each.
The incubation period of confirmed cases was 5.2 days, which may partially explain why cases occurred despite the use of infection control measures. For example, between April 14 and April 30, MERS-CoV infection was confirmed in nine patients who were undergoing hemodialysis. Of those, eight had an onset of disease before or within 24 hours after infection-control interventions were implemented on April 21.
The interventions included monitoring hand hygiene, implementing droplet and contact precautions for febrile patients, testing patients with fever for MERS-CoV, putting masks on all patients undergoing hemodialysis, not allowing patients with suspected MERS-CoV infection into the dialysis unit, enhancing environmental cleaning, and excluding visitors and nonessential staff. In perhaps a more troubling finding, eight days after implementation of precautions, illness developed in six patients:
“Acute viral respiratory tract infections cause considerable morbidity and mortality and pose a risk of outbreaks in health care settings,” the authors note. “We describe a cluster of MERS-CoV infections and report health care–associated human-to-human transmission of MERS-CoV. The 65% case fatality rate in this outbreak is of concern. We and others have found that the severity of illness associated with MERS-CoV infection ranges from mild to fulminant. The clinical syndrome is similar to SARS, with an initial phase of nonspecific fever and mild, nonproductive cough, which may last for several days before progressing to pneumonia. Some patients with MERS-CoV infection also had gastrointestinal symptoms, a finding similar to that with SARS.”