Nearly three dozen wild ducks have tested positive for the H5 bird flu (search) virus in Canada, officials reported Monday, but they said it was unlikely to be the strain blamed for more than 60 human deaths in Southeast Asia.

Dr. Jim Clark of the Canadian Food Inspection Agency (search) said it would take at least a week to determine whether the flu found in 33 ducks from the provinces of Quebec and Manitoba was the deadly H5N1 (search) strain that has ravaged Asian poultry farms.

But it was unlikely to be the same strain because none of the wild ducks tested was ill, he said at a news conference.

"That strain in Asia has caused high mortality in those birds; the birds that tested positive in Quebec and Manitoba are all healthy," Clark said.

Clark said 4,800 samples had been collected from wild birds in seven Canadian provinces in a study begun before the recent spread of H5N1 from Asia to parts of Europe and Turkey.

He said it was not surprising to find a variant of the H5 virus in Canada. He said it can be present in at least 7 percent of wild birds in North America at any given time, but in less virulent forms than the H5N1 strain.

The spread of H5N1 across the Eurasian land mass has world health experts worried about the possibility of a human flu pandemic developing that could kill millions and cripple economies.

The more a bird flu virus spreads, the more chances it has to mutate into a form that can pass easily from human to human. So far, all the deaths attributed to H5N1 have come in people who caught it from a bird.

The World Health Organization says the H5N1 outbreaks in Southeast Asia have infected 121 people and caused 62 deaths in Thailand, Vietnam, Indonesia and Cambodia. Vietnam has been hardest hit, with more than 40 deaths and tens of millions of poultry destroyed.

Less virulent strains of the H5 virus have been found before in North America. Parts of Mexico have suffered through an outbreak of H5N2 bird flu in poultry operations for more than a decade.

Canada had an outbreak of bird flu in 2004, but it was the less harmful H7 virus, which isn't believed to pose a serious risk to humans. About 17 million birds in British Columbia were slaughtered in early 2004 in an effort to stamp out any spread of the virus.