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A colorized transmission of the MERS coronavirus that emerged in 2012 is pictured.The Canadian Press

The spread of MERS coronavirus infections in hospitals in affected countries is a significant but underappreciated problem, infection control experts wrote in a journal editorial published Monday.

"The concentration of vulnerable patients, the frequent movement of patients, and the many daily contacts make health-care facilities the perfect breeding ground for MERS-CoV transmission," the authors warned in the journal Annals of Internal Medicine.

"Focus on the health-care setting may prevent continued human-to-human transmission among at-risk patients."

The authors are three specialists who travelled to Saudi Arabia last spring to investigate a large outbreak of MERS in a hospital at Al-Ahsa in the eastern part of the country. One of the three is Dr. Allison McGeer, head of infection control at Toronto's Mount Sinai Hospital.

Their publication came on the same day as the World Health Organization confirmed a doctor in Saudi Arabia had succumbed to the virus earlier this month.

The man, a Bangladeshi who practised in a Riyadh hospital, is not known to have had contact with a MERS patient or with the types of animals — bats and camels — suspected of being involved in the spread of the disease. He had not recently travelled outside the country.

As it remains unclear how people are contracting MERS, authorities would not be able to rule out the possibility the doctor caught the virus outside the hospital. But the possibility remains that he was infected while treating a patient who was not recognized as having been infected with MERS.

The editorial drew parallels to the role hospitals played in the spread of SARS — also a coronavirus — during the 2003 outbreak. McGeer was a key figure in Toronto's battle against that frightening new disease and she actually contracted the virus in the early days of the outbreak.

The authors cited a study published last fall that noted 30 of the first 161 known MERS patients were health-care workers. Since then at least two more health-care workers have become infected with the virus.

Just over a third of the health-care worker cases have been described as asymptomatic — showing no signs of illness. But a number of health-care workers have required intensive care treatment and at least three have died.

Health-care workers make up about 18 per cent of confirmed MERS cases so far. The WHO said Monday that there have been 180 confirmed cases to date; 77 of those patients have died.

In the SARS outbreak, health-care workers made up about 20 per cent of cases globally. In Canada, health-care workers comprised 43 per cent of probable and suspect SARS cases.

"I think there's a tendency to look at this and say 'Well, SARS was much worse.' And it's true. It's much better than SARS from a perspective of health-care workers," said McGeer.

"But there is still clearly too much serious illness and death in health-care workers. And to my mind until we solve where this is coming from, we can't effectively reduce that risk."

Michael Osterholm, an infectious diseases expert who has been following the MERS outbreak closely, said he believes people haven't grasped the scale of MERS health-care infections, perhaps because the outbreak to date has remained in countries on the Arabian Peninsula.

Toronto's large SARS outbreak really drove home for western countries the risk the new disease posed, said Osterholm, who is the director of the Center for Infectious Diseases Research and Policy at the University of Minnesota.

"If we had a situation where we had a sizable outbreak in the western world, where 17 to 20 per cent of the cases where in health-care workers, I think you'd be seeing a very different attitude towards the concern about health-care workers and MERS."

The editorial was published in conjunction with a report on the disease course and symptoms of 12 MERS patients treated in the intensive care units of two Saudi hospitals. Three of the 12 were health-care workers.