"Over the past few weeks, we have seen a surge in the number of influenza cases across Alberta. Many of those affected are healthy young adults," Health Minister Fred Horne said in a statement.
In total, 965 cases of the flu have been confirmed by health authorities in the province, with just more than 250 requiring hospitalisation, he explained.
"Sadly, five Albertans admitted to the ICU have died," Horne said, emphasising that the age and health of the patients was unusual.
So far, only around one in five residents have gotten flu shots, which, Horne emphasised, are needed to protect "you, your friends, family, co-workers and everyone you come into contact with.
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"That includes vulnerable Albertans for whom the flu can mean serious illness or even death," he stressed.
To encourage vaccination efforts, the province has increased the number of centres offering the shot and extended the hours. Local television showed long lines in the cities of Edmonton and Calgary.
The peak of the flu season typically comes in February, according to health authorities who fear a surge in cases that could overwhelm health centres.
The outbreak is also starting to spread to other provinces, and one person reportedly died from the flu in Ontario.