06/11/2013 04:49 EDT | Updated 08/11/2013 05:12 EDT

International collaboration needed to find elusive source of MERS virus

TORONTO - International collaboration will be needed to find the source of the elusive MERS virus, says a Canadian SARS expert who has been involved in efforts to investigate and contain an outbreak of the new coronavirus in Saudi Arabia.

Health officials in the kingdom have put a lot of work into finding and containing the virus — more work, actually, than has been publicly disclosed, Dr. Allison McGeer said in an interview.

But she said with comparatively few cases to investigate spread out over a number of countries, puzzling out where the virus lives in nature and how people are contracting it will take a bigger effort than has been made to date.

"The Kingdom of Saudi Arabia has done a lot of work in the investigation of both the human-to-human transmission (cases) and the source of community infections, but it's very clear that a great deal more work needs to be done," said McGeer, who just returned from her second MERS-related trip to Saudi Arabia.

"And that a very substantial amount of international collaboration is the only way that we're going to be able to move knowledge about this virus forward at the speed that everybody wants to see it move."

McGeer was one of the members of a World Health Organization-led mission to Saudi Arabia to investigate the country's MERS outbreak. The team concluded its six-day mission on Sunday. On Monday, it released a statement warning health-care workers around the globe to be on the lookout for the new virus because of its proven capacity to spread.

McGeer, who is head of infection control at Toronto's Mount Sinai Hospital, also travelled to Saudi Arabia in May at the request of the Saudi government to help investigate an outbreak in a hospital in Al-Ahsa, in the eastern part of the country. McGeer was a major player in Toronto's SARS response in 2003 and even contracted the virus during the early days of the virus's spread through city hospitals.

The SARS and MERS viruses are cousins, both members of the coronavirus family.

McGeer said it appears the hospital-based outbreak in Al-Ahsa may be over, though there is still one facility where there remains a possibility of additional cases caused by person-to-person spread.

Saudi officials have to date only publicly acknowledged spread in one or possibly two hospitals in Al-Ahsa. McGeer said in fact the Al-Ahsa outbreak has involved person-to-person spread in several hospitals, though she declined to specify how many facilities have been involved.

"In the majority of facilities, the outbreak appears to be under control, although it's really important to recognize that because this (disease) has a long incubation period, that you can't declare an outbreak over (too soon)," she said.

"One of the lessons from SARS was about not declaring an outbreak over until a long enough period of time has passed."

In Toronto, an assumption that spread of SARS had been interrupted led the Ontario government to declare victory against the virus in mid-May of 2003. Hospital workers were told they no longer had to wear the N-95 respirators that shielded their mouths and noses and many quickly doffed the hot and cumbersome equipment. Within days, sick health-care workers started to show up in emergency rooms, signalling the virus was still spreading in the city's hospitals.

McGeer suggested the fact that the Al-Ahsa outbreak appears to be coming under control is good news for those concerned about the spread of the virus to other parts of the world — or at least to parts of the world with strong health-care systems. The WHO has voiced concerns about the possibility that guest workers — citizens of Bangladesh, the Philippines and other parts of Asia who work in Saudi Arabia — could take the virus home with them and trigger outbreaks in less developed countries.

"The hospital person-to-person transmission appears to be manageable. It may not be easy. But it appears to be manageable, at least in the developed world," she said. "But the critical piece of understanding this virus is understanding what the reservoir is and how people get infected in the community."

McGeer offered some insight into why that is proving to be such an enormous — and frustrating — challenge.

While there have been 55 confirmed cases of MERS, in reality there have been relatively few cases that could be described as index cases — people who were infected by contact with the virus's source. Quite a few of the cases — McGeer would not say how many — have likely been infected through limited person-to-person spread.

That latter type of case can teach public health officials about the conditions under which the virus can spread from person to person. But to find the source of the virus, they have to investigate cases where it is clear the infection came from a non-human source. And with relatively few such cases, spread over a number of countries, co-ordinating the search has proved difficult, she said.

"We get back to there's a really small number of cases, they're in a bunch of different countries, the process of doing the exploratory work to figure out what exposures might be important has to happen with people ... on the ground in all those countries talking to each other on a regular basis," McGeer said.

"That's not something we're set up to do. It's really hard to get that organized and working well."

Adding to the complexity is the fact that a successful epidemiological investigation will require someone who understands the culture of the countries in which infections are taking place, someone who can decipher the clues seen in the pattern of cases to date. Most have been in men. Many cases have been seen in travellers — men from Britain, Italy and Tunisia who travelled to Saudi Arabia, a man from France who travelled to the United Arab Emirates.

"There's a bunch of hints in the data we have so far about the cases. But that's exactly what they are," McGeer said. "And they do help to some degree guide how you should do the investigation. But they're not enough for somebody to say: 'Ah! It's the dates.'"

Saudi Arabia's Eastern Province is a major date-producing area, and people have mused about the possibility that virus from bats may be contaminating dates in some way. (The genetic sequence of the virus suggests it originated in bats.) But McGeer noted it isn't currently date harvest time.