OTTAWA - Canada's chief public health officer says the country has seen the worst of the swine flu - for now.

Dr. David Butler-Jones said Monday it appears that spread of the virus is waning. "It looks at this point like we're over the worst of it in Canada for this season," he said.

"But, again, I'm going to hedge my bets on that because we're watching very closely and it's still within the incubation period of previous cases, so you could see a second spike."

There has so far been a confirmed total of 520 cases - including one death - of the strain of H1N1 in Canada. Nearly all the cases have been mild.

The virus seemingly peaked around the end of last month and the beginning of this one, Butler-Jones said.

"Once we've been a couple of weeks past the presentation of cases, etc., and we see the numbers, then we can say with some confidence that we're over the worst," he said.

"We seem to be trending in that way, but we'll have to wait and see over the next few days."

Some health officials have suggested the virus isn't likely to peter out over the summer as flu strains tend to do when the mercury soars in the Northern Hemisphere.

Butler-Jones didn't rule out more cases over the summer and a resurgence in the fall.

"We are suspecting that this will be back in the fall given how widely it's spread so far," he said.

"We need to be planning for that, including the development of vaccines and other things."

The federal government has signed a contract with pharmaceutical giant GlaxoSmithKline to produce a new vaccine for swine flu when one is developed, Butler-Jones said. Every Canadian is covered for two doses of the vaccine under that deal.

Federal scientists are working on a vaccine strain at the National Microbiology Laboratory in Winnipeg.

In a further sign that spread of the swine flu virus is tapering off, Ottawa lifted its advisory against non-essential travel to Mexico on Monday as flu cases there start to level off.

The federal government says travel to Mexico - the epicentre of the swine subtype of H1N1 - is no longer a risk to Canadians since the virus has been spreading through Canada for some time.

The Canada Border Services Agency will continue to visually check travellers for signs of illness.

But the Public Health Agency of Canada will cease some Mexico-specific travel measures such as distributing health alert notices to passengers on direct flights to Mexico and having quarantine officers meet every direct flight entering Canada from Mexico.

News of the travel advisory being lifted comes as Health Minister Leona Aglukkaq attends the annual World Health Assembly meeting in Geneva, Switzerland.

Several countries - including China, Britain and Japan - urged the World Health Organization against raising the swine flu alert to the highest level.

WHO Director General Dr. Margaret Chan agreed to keeping the alert level at the current Phase 5 out of a possible six - one level short of a worldwide pandemic.

Aglukkaq said Canada was one of the countries in Geneva pushing for the WHO to take into account whether the virus was causing severe or mild illness, not just how quickly it was spreading.

"It has been raised by other countries, as well," she said. "Canada is not alone in those thoughts."

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