Official start of flu season will likely be declared this week: PHAC

A patient receives an influenza vaccine in Mesquite, Texas, on Thursday, Jan. 23, 2020. THE CANADIAN PRESS/AP/LM Otero

The official start to the flu season is set to arrive any day now, according to federal health authorities.

The latest data on influenza trends found that the rate of positive cases was 6.8 per cent, which is higher than the seasonal threshold of five per cent positivity.

“If percent positivity remains above this threshold next week, the start of the influenza season will be declared at the national level,” states the latest FluWatch report from the Public Health Agency of Canada (PHAC).

The report, released early last week, looked specifically at the rate of influenza circulating in the community for week 46 of 2023, Nov. 12 to Nov. 18. During that week, a total of 1,849 laboratory detections of influenza were reported to PHAC, with the vast majority of them being cases of influenza A.

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Between the end of August and Nov. 18, a total of 51 laboratory-confirmed outbreaks of influenza have been reported, with 10 of these reported in the most recent week of data alone.

In that same 11-week time period, there were 332 influenza-associated hospitalizations reported across Canada by participating provinces and territories, with 46 per cent of these hospitalizations being among adults aged 65 years or older. There have been 11 influenza-associated deaths reported since the end of August.

The 51 outbreaks of influenza were all driven by influenza A, although one outbreak was mixed with cases of the less common influenza B. Of the 51 outbreaks, 32 took place in long-term care facilities.

Another sign that the official flu season is just around the corner is that the number of regions reporting influenza activity is increasing, both in number and in intensity of the activity.

In week 46, six provinces reported localized influenza activity, while Alberta reported widespread activity, largely in the northern region of the province.

That week also saw 90 influenza-associated hospitalizations, which is more than a quarter of all hospitalizations since the end of August.

Around two per cent of all visits to healthcare professionals during that week were due to influenza-like illness, the report stated, although it added that there is a smaller number of people gathering this data now.

FluWatch also assesses how common certain symptoms are through volunteer participants. In week 46, more than 9,000 Canadians contributed this information to FluWatchers, with 1.9 per cent reporting symptoms of cough and fever. Of those who reported cough and fever, one fifth consulted a healthcare professional and 81 per cent reported missing days from work or school as a result of their illness.

The report noted that the symptoms of cough and fever occur across various respiratory illnesses, including COVID-19, RSV and the common cold, and the metrics of these symptoms help to give an idea of how much respiratory illnesses are circulating at a time when there are multiple viruses active.

A graph depicting the arc of previous flu seasons showed that current rates are falling along the average increase that we would expect to see at this time of year. Historically, the flu season can occur at some point anywhere from late October to late May.

Last year, Canada experienced an early peak of flu cases, with the positivity rate reaching above 20 per cent by early December and then dropping over the next few weeks.