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H5 Found in Wild Birds in Canada; Testing Needed to See If is Asian H5N1

Posted on: Monday, 31 October 2005, 15:01 CST

By HELEN BRANSWELL

(CP) - Several wild birds in Quebec and Manitoba have tested positive for H5 flu viruses, but officials were quick to reassure Canadians on Monday that it's not necessarily the dangerous H5N1 strain that has caused human illness in Asia.

Officials said they don't know yet if the birds - 28 in Quebec and five in Manitoba - have the H5N1 subtype of the avian flu. Even if they do, it might not be the exact strain responsible for lingering poultry outbreaks and human infection in southeast Asia.

"It's important to clarify that the avian influenza virus is not new to wild birds," Jim Clark of the Canadian Food Inspection Agency told a news conference in Ottawa.

Officials tested 800 wild birds from six sites across the country in September and October, said Dr. Ted Leighton of the Canadian Co-operative Wildlife Health Centre at the University of Saskatchewan.

A senior government source told The Canadian Press about 40-50 per cent of those birds tested positive for an avian influenza and a "small fraction" have an H5.

Health officials in Winnipeg conducting tests on the H5-infected birds won't know til mid-week whether they have H5N1 - by far the worst known avian flu virus when it infects humans.

The official World Health Organization count suggests there have been 137 cases since 1997, when it first jumped into humans. Of those known cases, 67 died.

H5 avian viruses have been found before in North America. Parts of Mexico have suffered through an outbreak of H5N2 avian flu in poultry operations for more than a decade.

There are nine known neuraminidases - the N in a flu virus's name. So scientists will need to type these viruses to better determine what they are.

Even if the Canadian birds have the H5N1 virus, it doesn't mean they are necessarily closely related to the viruses behind the Asian outbreaks.

Studies of genetic sequences of avian influenza viruses over the years have shown that the North American viruses seem to be distinct from the Eurasian viruses, suggesting there isn't a lot of co-mingling of viruses.

"For whatever reason the North American and Asian lineages of flu have remained quite distinct for a long period of time," the source said.

If the Canadian birds turn out to have H5N1 viruses, genetic sequencing must be done to determine whether they are related and how closely related before officials could say whether wild migratory birds had brought the virus to North America.

Source: Canadian Press

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