The woman is believed to have contracted the infection in China, where she spent most of December in Beijing.
She was ill on her return to Canada on Dec. 27, was hospitalized on Jan. 1 and died on Jan. 3.
One of the WHO's flu experts says the agency would like more information on her illness, because initial reports have suggested her symptoms were not entirely typical of H5N1 infections.
Dr. Nikki Shindo says the agency would like to know if there has been an autopsy or if one is planned.
Autopsies can yield a wealth of information about a disease but are not commonly done and are frowned on by some cultures.
It wasn't immediately known if an autopsy was conducted in this case.
Alberta's Chief Medical Officer, Dr. James Talbot, has said the woman had neurological symptoms that made doctors suspect she had encephalitis, or a brain infection.
While that isn't a common symptom of flu it can happen, and has been reported in some H5N1 cases.
In fact, Dr. Keiji Fukuda, the WHO's top flu expert, says when he heard of the case, he was struck by the reference to encephalitis.
The first known person infected with H5N1 — a three year old boy in Hong Kong in 1997 — showed signs of encephalopathy, says Fukuda, who helped investigate that outbreak.
Shindo says the WHO has gotten preliminary information on the case, but hopes to learn more on Friday about the steps China and Canada will take to try to figure out how the woman became infected with the bird flu virus.
There have been no recent H5N1 outbreaks reported by China, but the timing of the woman's symptoms suggest she must have been infected there.
Shindo says Chinese authorities have been looking aggressively for non-human influenza A viruses because of the country's more recent problems with H7N9 — another bird flu — so it is somewhat surprising to see an H5N1 case like this pop up.
Fukuda says the likelihood is that this will turn out to be a one-off case, with the woman having been infected by exposure to a bird or a contaminated environment. But piecing together how that exposure occurred may be difficult.
"We usually ask people about poultry exposure, poultry market exposure and all of those things," he says. "But from the beginning, there has always been a percentage of people that we haven't really known how they got infected."
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