- In a matter of a few years, the term Norwalk virus has
become part of the public lexicon. At this time of year, it seems like
it's everywhere: grounding planes and closing daycares, spreading misery
in long-term-care facilities and schools.
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- Infectious-disease experts say they think outbreaks are
more common and there's something changing in the behaviour of the nasty
noroviruses.
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- "We certainly believe that what we've seen over
the last five years is an increase in the activity of this virus,"
said Dr. Paul Sockett of the Public Health Agency of Canada.
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- "And this is early stages yet but we have some evidence
which suggests that we may have a slightly more virulent strain that's
been circulating in the past couple of years," he said, adding the
bug has been sowing misery "fairly well across the country."
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- Dr. Sockett, who works in the agency's centre for infectious-disease
prevention and control, acknowledges the increase may be partly attributable
to the fact that public-health officials are paying more attention to noroviruses.
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- But he believes the increase in cases reported to laboratories
across the country can't be explained away by more vigilant reporting --
there were 300 to 400 reports a year in 2003 and 2004, up from a mere 14
in 1998.
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- Dr. Sockett's observations confirm concerns being voiced
by infectious-disease specialists, who have been worried by the apparent
explosion of outbreaks caused by noroviruses -- the family to which Norwalk
and Norwalk-like viruses belong.
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- Infectious-disease specialist Dr. Michael Gardam was
one of those who suspected something about the norovirus situation had
changed, noting it has grounded planes and brought cruise ships to dock.
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- "If you think about what's happened to the cruise
industry -- that didn't happen 10 years ago. That really is something that
seems to be fairly new," said Dr. Gardam, director of infection prevention
and control at Toronto's University Hospital Network. "There's no
doubt Norwalk seems to be a bigger player than it was six years ago."
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- But Dr. Gardam admitted that's a gut feeling -- a gut
feeling that in the recent past would have been impossible to prove.
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- He and others acknowledge the sense of increased activity
could be, at least in part, due to greater attention being paid to noroviruses
because of the havoc they wreak in hospital settings and because it is
now easier to study the viruses.
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- Until recently, there was little incentive for doctors
or hospitals to send stool samples for testing for norovirus. They could
diagnose from clinical symptoms and knew that while the disease was miserable,
it was rarely life-threatening.
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- And there was little point to sending samples to the
lab; the virus can't be grown in culture, so there was no way to produce
a viral isolate to study.
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- With the development of polymerase chain-reaction testing,
laboratories can now amplify pieces of the virus and produce a genetic
fingerprint that can be compared to the fingerprint of other noroviruses.
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- That opens up research possibilities that need to be
explored, said Dr. Allison McGeer, head of infection control at Mount Sinai
Hospital in Toronto.
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- "The argument for not studying them is people don't
die from them very often... but from an institutional-disruption point
of view, they're expensive as all get out," she said.
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- "And I think that means we've got to sit down and
figure out what we're doing with them."
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- The Public Health Agency is trying to do just that. Last
week it convened a meeting of provincial and territorial public-health
officials to try to get a handle on the problem.
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- "Certainly one of the things we would like to do
is to sort of collect the different strains and catalogue them and see
where they're appearing in the country to see if there's any connect between
them and what types of evolution in those strains are taking place,"
Dr. Sockett said.
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- The laboratories of the British Columbia Centre for Disease
Control have been doing that type of tracking for the past four years,
producing Canada's first database of about 350 viral fingerprints dating
back to 1994 from frozen stool samples.
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- They've seen a dominant strain, said Dr. Judy Isaac-Renton,
director of laboratory services. It was the seventh strain they typed in
2002; they called it 007.
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- "We always have a picture of James Bond on it because
it has the licence to ill," Dr. Isaac-Renton said with a chuckle.
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- Having viral fingerprints allows public-health authorities
to track the progress of particular viruses, but the science hasn't yet
evolved to the point where they can tell if one causes worse disease than
another, she noted.
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- But Dr. Isaac-Renton does believe the pattern of disease
has changed, with a worrisome increase of norovirus outbreaks in health-care
institutions.
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- "It's changing in the sense that it's now impacting
very severely ill people in acute-care hospitals. And to me that's a significant
change."
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