Canada's flu season has arrived roughly seven weeks ahead of schedule, and health officials are urging residents to get vaccinated as doses reach clinics and pharmacies. According to Health Canada data, about six per cent of influenza tests came back positive in the week ending Oct. 17, compared with less than one per cent a year earlier.

Why is the flu season starting early?

Experts say the exact cause is unclear. Dr. Brian Conway of the Vancouver Infectious Disease Centre told Global News the virus may have arrived via the Pacific Rim, possibly from the southern hemisphere, and entered through the West Coast. Dr. Isaac Bogoch of Toronto's University Health Network said the timing is early but not outside the usual range.

British Columbia is currently the hardest-hit province. Positivity there ranged from about 10 to 18 per cent in mid-October, while Alberta, the territories and other provinces reported low or very low activity. Some experts caution that differences in testing rates between provinces may distort the picture.

What are the current risks?

The dominant strain this year is H1N1, the subtype behind the 2009 swine flu epidemic. Doctors note that H1N1 seasons typically bring fewer hospitalizations than H3N2 seasons, but stress that influenza can still cause severe illness in any individual. A genetic mutation of H1N1 that helps the virus evade immunity has been identified in the United States; Dr. Jesse Papenburg of Montreal Children's Hospital said he has not heard of it appearing in Canada.

How can people prepare?

Health authorities in several provinces are urging eligible residents to get flu, COVID-19 and RSV vaccines.

  • In Manitoba, flu and COVID-19 shots are free for everyone six months and older.
  • RSV vaccine is offered to infants in their first season, some people aged 60 to 79 in congregate settings, and those 80 and older.
  • In British Columbia, officials say nearly two million flu doses and 1.5 million COVID-19 doses have been secured.

Some Montreal pharmacies ran out of initial supplies in the first week of the provincial campaign, and officials are asking people to be patient.

FAQ

What is the epidemic threshold for flu?

Health Canada sets the threshold at five per cent of tests positive, a mark the country did not reach until mid-November last year.

Who should get vaccinated?

Officials encourage everyone eligible, especially those most at risk, to get a flu shot; eligibility for RSV and COVID-19 doses varies by province.