OTTAWA - Canada's agriculture minister says pork remains safe to eat despite a warning by the World Health Organization that the swine flu virus may survive freezing and could be in the thawed meat and blood of infected pigs.

"Canadian pork is safe. There is no danger. Bottom line: Canadian pork is safe," Gerry Ritz said Wednesday after serving up pork sandwiches to MPs and government workers at a luncheon on Parliament Hill.

The WHO's warning came as Canadian scientists confirmed the swine flu spreading through Canada and Mexico is the same strain - even though it has killed 42 Mexicans and been relatively mild here.

Earlier in the day, however, a WHO official told Reuters the blood of pigs infected with a swine subtype of H1N1 may contain the virus.

Jorgen Schlundt, director of WHO's Department of Food Safety, Zoonoses and Foodborne Diseases, said it's possible for influenza viruses to survive the freezing process and be present in thawed meat and blood.

Schlundt cautioned against eating meat from sick and dead pigs infected with the swine flu.

Canada has safeguards to keep diseased pigs from making it to market, said the country's top veterinary officer, Dr. Brian Evans of the Canadian Food Inspection Agency.

Those checks make it virtually impossible for infected pork to end up on store shelves, he added, since pigs are screened on farms for illnesses before they ever make it to the slaughterhouse.

Swine also undergo a clinical pre-assessment at slaughterhouses, and pig parts are checked again on the processing line.

"The message that is coming out clearly from WHO today, which is standard operating practice in Canada, is the fact that you do not slaughter sick animals and you do not slaughter dead animals for human consumption," Evans said.

"This doesn't change anything in Canada. What the WHO is saying is what we do every day, every week, every month, every year as part of our food inspection system."

Added Canada's chief public health officer, Dr. David Butler-Jones: "There is no reason to stop eating pork. The inspection system in Canada does address all those issues."

What becomes of infected pigs on an Alberta farm remains uncertain.

Some 220 pigs in the herd of 2,200 showed flu symptoms on April 24 after a farmhand who travelled to Mexico and fell ill upon his return apparently infected them with the H1N1 virus.

All of the pigs are recovering or have recovered. The barn has been under quarantine since April 28, and no other area hog barn has so far been affected.

The Canadian Food Inspection Agency is monitoring and testing the herd, Evans said. The CFIA has not yet decided whether to cull the herd.

No one has caught swine flu from eating pork.

But 10 countries have banned Canadian pork products since the virus was found on the Alberta farm. China in particular banned pork from Alberta.

Canadian politicians and health officials have appealed to countries to lift the pork ban, which producers fear could do to their industry what the 2003 BSE outbreak did to the Canadian cattle industry when exports were shut down for more than a year.

In 2008, total Canadian pork exports were valued at $2.7 billion, including nearly $527 million worth of live swine exports.

Also Wednesday, officials said researchers at the National Microbiology Laboratory in Winnipeg are the first to genetically sequence Canadian and Mexican samples of the H1N1 virus.

And they have ruled out a mutation to explain why the Mexican cases have been much more severe than elsewhere.

One possibility being considered is that the Mexican victims may have had underlying medical conditions that made them more susceptible to the bug.

Canada's cases have all been mild, with the exception of a young Alberta girl who came down with a severe case of the flu.

Frank Plummer of the National Microbiology Laboratory said scientists worked day and night to sequence the virus in less than a week.

"We're continuing our analysis, but essentially what it appears to suggest is that there's nothing at the genetic level that differentiates this virus that we've got from Mexico and those from Nova Scotia and Ontario that explains apparent differences in disease severity ...

"That's one of the big questions that everybody's been asking, so part of the answer is that it's likely not the virus itself that is explaining the differential and severity of disease between Mexico and the rest of North America."

Plummer said he hopes the breakthrough will help to identify origin of virus and reveal how it spreads and mutates.

Officials have said Canada's only severe case - involving a girl in an Edmonton hospital - had more to do with underlying conditions than it did with the virus itself.

The girl, who has not been identified, is getting better and is breathing on her own.

It remained unclear how the girl, whose age was not released, became infected.

Canada now has 183 confirmed cases of swine flu.

Nova Scotia reported five new cases Wednesday, bringing the province's total caseload to 53.

Ontario is confirming 13 new cases of the swine flu, bringing the total number of cases in the province to 49.

All of the new cases are said to be mild.

The new cases were spread out across the province in communities such as Toronto, London, Windsor and Sudbury. Thirty women and 19 men in Ontario have contracted the virus.

The federal Public Health Agency's website says the common flu sends about 20,000 Canadians to hospital each year. Between 4,000 and 8,000 can die of influenza and its complications annually, depending on the severity of the season.