The person, whose name and age were not revealed, was reportedly feeling ill on Dec. 27 while flying from Beijing to Vancouver and then on to Edmonton. The patient was admitted to hospital on Jan. 1 and died Jan. 3.
Federal public health officials said confirmation of the rare exported H5N1 infection was made Tuesday evening and Canada informed officials of the World Health Organization on Wednesday.
Health Minister Rona Ambrose, who took part in a hastily assembled news conference in Ottawa, said the case is likely to be an isolated one.
"The risk of getting H5N1 is very low," Ambrose said. "This case is not part of the seasonal flu, which circulates in Canada every year."
The discovery of a case of H5N1 so far afield was already garnering international attention Wednesday. But flu experts said that in some ways, the novelty isn't that a case was found here, it was that such an event hadn't happened sooner.
"I'm surprised we haven't seen at least one importation before now into North America ... given the connectedness that we have with that region," said Dr. Danuta Skowronski, an influenza expert at the British Columbia Centre for Disease Control
"We've been preparing for an incursion for over a decade," acknowledged Dr. Theresa Tam, head of the Public Health Agency of Canada's health security infrastructure branch.
"It's actually much rarer than we had ever thought. This is the first case in this whole continent."
Officials did not release the name of the patient, nor did they indicate how old the person was, where he or she lived in Alberta or whether the person is a he or a she. During the news conference, the term "she" was used several times, but it wasn't clear if that was a slip and officials insisted they would not confirm the person's gender.
Contacts of the Alberta resident, as well as the health-care workers who cared for the patient, are being monitored for signs of illness but to date there does not appear to have been onward transmission of the virus. They have been offered the antiviral drug Tamiflu, which can be taken to prevent infection as well as to treat it.
"None of them have symptoms and the risk of developing symptoms is extremely low," said Dr. James Talbot, Alberta's chief medical officer of health. "Precautions for health-care staff were also taken as part of this individual's hospital treatment."
The Public Health Agency will be contacting passengers who were on the same flights as the Alberta traveller to check on their health. But Dr. Gregory Taylor, Canada's deputy chief public health officer, said it was unlikely transmission occurred on the planes.
The person travelled on Air Canada flight 030 from Beijing to Vancouver, and Air Canada 244 from Vancouver to Edmonton. Both flights were on Dec. 27.
Dr. Perry Kendall, British Columbia's chief medical officer, said the person spent about two and a half hours in Vancouver International Airport waiting for the connecting flight and was there from about 12:30 p.m. PST to 3 p.m. PST. He too suggested it was unlikely that the infected person transmitted the virus to others en route.
In fact, flu experts were viewing the event as interesting, and a useful reminder that international travel can spread infectious diseases around the globe. But they weren't unduly concerned.
"Every H5N1 case makes you nervous. But I don't think it should be a cause for alarm," said Dr. Allison McGeer, head of infection control at Toronto's Mount Sinai Hospital.
"It's good that people are watching for it. Brilliant that people identified the issue and made the diagnosis."
Figuring out what was behind the illness wasn't easy.
The patient had what is being described as an atypical presentation — fever and headache, which are symptoms of flu, but no cough, which is common in influenza cases.
The person went to hospital on Dec. 28 but was sent home after being examined. The illness progressed rapidly and the person returned to hospital on Jan. 1 and was admitted. On Jan. 3, he or she died.
In an interview with The Canadian Press, Taylor said initially it was thought the person had a clot in the lung — a pulmonary embolism — but that was ruled out. And after the first visit to hospital by the person, on Dec. 28, the patient was sent home.
The health-care team caring for the patient also thought the person might have meningococcal encephalitis, an infection of the brain.
But a chest X-ray showed signs of pneumonia and the unidentified hospital ran a battery of tests. The influenza A test came back positive, as did one for a human coronavirus, one of the causes of common colds. The team wondered for a time if the severity of the illness was due to the co-infection with two viruses.
On Jan. 5, Taylor received a call from Talbot, who said tests showed the flu virus was not one of the seasonal influenza A viruses. Alberta was going to send a sample to the National Microbiology Laboratory in Winnipeg to get their help.
The specimen arrived in Winnipeg on Tuesday morning. By that evening the Alberta lab had identified the virus as an H5; it didn't have the capacity to identify which neuraminidase or "N" number the virus had. Almost simultaneously, the Winnipeg lab's testing got the full result: H5N1.
Tam said the national lab will share the virus with the WHO's network of influenza collaborating laboratories, but Canada is certain of the test result.
"We're very confident this is the diagnosis," she said.
Taylor said the Public Health Agency is also liaising with China and hopes to investigate with it how and where the person was exposed to H5N1. It is currently thought the person did not travel outside Beijing, where there have been no recent reports of H5N1, in birds or in people.
The virus is endemic, though, in parts of the country and continues to spread in a number of countries in Asia and the Middle East.
This virus was first spotted in 1997, in an outbreak in which 18 cases — six of them fatal — were reported. But after that flare up was contained the virus appeared to vanish.
It returned with a vengeance in early 2004, igniting a large multi-country outbreak that continues to this day. Since then nearly 650 human cases have been reported from now 16 countries.
While the virus does not often transmit to people, it can cause severe illness when it does. About 60 per cent of known cases have died from their infections.