Mexico - ground zero in the global flu outbreak - is all but sounding the all-clear. Experts say pork is safe to eat, but Alberta pigs have some turning up their noses. And perfectly healthy Canadians are among a group of tourists under quarantine in China.

The truth, it seems, has become a casualty of the world's war against swine flu.

Contradictions were rampant on the outbreak front Monday, particularly in Canada, where a sharp jump in the national caseload to 140 - including a "severe" case involving a young Alberta girl in an Edmonton hospital - left Mexico's optimism seeming misplaced.

"This case underscores a couple of things about influenza: it has few boundaries, it doesn't respect borders, (and) it often doesn't respect age," said a stern-faced David Butler-Jones, Canada's chief medical officer of health.

"It is a very, very serious disease that takes its toll on people, young and old, so we need to stay vigilant."

Officials in Mexico, where the outbreak alert level was lowered Monday to orange from red, seemed to feel differently. In Mexico City, restaurants, amusement parks and museums were poised to re-open later this week after several days in self-imposed exile.

"Mexico is trying to return to normalcy as soon as possible," a defiant President Felipe Calderon said in an interview that aired Sunday. "We are going to win this battle."

A world away, an excess of vigilance was on full display in China, where two developments - a ban on Alberta-bred pork after some pigs tested positive for the virus and the quarantine of several Canadian tourists who did not - struck some as irrational and unjustified.

Foreign Affairs spokesman Alain Cacchione said Canadians were among those at the Metro Park Hotel in the Wanchai district of Hong Kong who were placed under "preventative medical surveillance" on the weekend after a guest tested positive for the virus.

Some 29 students from the Universite de Montreal, all but six of them Canadian, were meanwhile in preventative quarantine in a hotel in the city of Changchun in northern China after arriving there from Montreal, officials said.

"I think the quarantine was in the cards regardless of what symptoms they had," said David Ownby, director of the university's East Asian studies program, who characterized the situation as little more than wrong place, wrong time.

"They had no symptoms whatsoever."

In Ottawa, Liberal foreign affairs critic Bob Rae grilled the government about China's decision to quarantine Canadian citizens.

"It would seem that there has been no justification, no public health reason on the part of the Chinese government," Rae said during Question Period.

Officials from the Canadian consulate in China have been asked to make sure those in quarantine there are being treated well, Foreign Affairs Minister Lawrence Cannon said.

Mexico, too, was angry - not only for the quarantining of its citizens, but also for what it described as the singling out of Mexican nationals and for the arbitrary banning of flights from Mexico by Argentina, Peru and Cuba.

"I think it's unfair that because we have been honest and transparent with the world, some countries and places are taking repressive and discriminatory measures because of ignorance and disinformation," Calderon said.

For Alberta's hog producers, the Chinese ban on pork was more a slap in the face than a blow to the gut. The big fear, they said, was of the United States, already in "Buy American" mode thanks to the ongoing economic crisis, closing its doors.

"That's the one (domino) we don't want to fall," said Florian Possberg of Canada Pork International, an organization charged with keeping markets open for Canadian products.

"The fact the U.S. has maintained our trading relationship has been very helpful for us."

Canada sends six million hogs to the U.S. - its only market for live pork product - each year, Possberg said. In 2008, total Canadian pork exports were valued at $2.7 billion, including nearly $527 million worth of Canadian live swine exports.

China and at least eight other countries on four continents banned Alberta pork after reports surfaced this weekend that 220 hogs had been quarantined after being passed theH1N1 virus earlier this month from a worker who had been in Mexico.

The ban on Canadian pork is far from the only display of outbreak-induced irrationality. In Egypt, a predominantly Muslim country where pigs are raised and pork consumed solely by the country's Christian minority, every one of the animals has been ordered killed.

"China is operating outside of sound science," federal Agriculture Minister Gerry Ritz said Monday during Question Period.

"We're looking for clarification as to why they've gone as far as they have."

International Trade Minister Stockwell Day denounced the ban as "disappointing and unwarranted," and said Canadian officials are making the rounds to make sure those countries that have banned pork imports are aware of the facts.

U.S. Agriculture Secretary Tom Vilsack has said the United States has no plans to alter its trade policies regarding Canadian pork.

The outbreak has cost the pork industry in the U.S. an estimated US $3 million a day, said Dave Warner of the Washington-based National Pork Producers Council.

"They're trying to protect their domestic markets, but they know that the viruses are not food-borne, they're respiratory, so they know this is a bogus issue," Warner said of the trade bans.

"We will ask that the border be allowed to be kept open for pig movements. We're satisfied that the virus in that one herd was contained."

Reports Monday that the World Health Organization was poised to move its six-tiered alert level to Phase 6 - that of a full-blown pandemic - proved premature. as the UN health agency urged governments to apply common sense to their containment efforts.

"Let me make a strong plea to countries to refrain from introducing measures that are economically and socially disruptive, yet have no scientific justification and bring no clear public health benefit," WHO director-general Margaret Chan said in a video message to the UN General Assembly in New York.

If or when Phase 6 is reached, quarantines will be largely pointless, WHO flu chief Keiji Fukuda suggested.

"As we get later on into Phase 6 then these sorts of measures will become less useful," he said. "There will just be more infections around, and you can't quarantine everyone in the world."

Raising the alert level to Phase 6, the highest, would mean that a global outbreak of swine flu is underway. WHO uses the term pandemic to refer to geographic spread rather than severity. Pandemics aren't necessarily deadly. The past two pandemics - in 1957 and 1968 - were relatively mild.

"We do not know how long we will have until we move to Phase 6," Chan said.

"We are not there yet. The criteria will be met when we see in another region outside North America, showing very clear evidence of community-level transmission."

More than 1,000 people have been sickened worldwide, according to health and government officials.

-With files from The Associated Press