Latest flu report: Influenza B on the rise in Canada

Influenza levels have increased slightly across Canada in recent weeks – notable less for the overall numbers and more for the fact that they’re driven entirely by a rise in influenza B cases, according to Canada’s FluWatch.

The report, which comes out weekly and tracks confirmed influenza cases across the country, stated that in Week 13 of 2023, a total of 510 laboratory detections of influenza were noted across the country, numbers that aren’t out of the ordinary for this time of year.

Of these confirmed flu cases, 364 were due to influenza B and 146 were due to influenza A. Read more about the different viruses from Health Canada.

This means influenza B is currently making up 71 per cent of detections — a change from influenza A’s dominance in 2022.

The percentage of tests that came back positive for influenza were 2.4 per cent in Week 13, up from 0.8 per cent in Week 7, an increase solely due to the bump in influenza B, according to the latest FluWatch.

The strain is circulating at much higher levels currently than it was last year.

During the height of flu season at the end of 2022, the vast majority of cases were due to influenza A, with influenza B barely making a dent.

And in March-April of last year, there were only four cases of influenza B across five weeks of flu surveillance, compared to 1,283 cases of influenza A.

There were 15 pediatric hospitalizations related to influenza in Week 13, 14 of which were due to influenza B.

The overall levels of influenza being seen right now, including all strains, are typical for interseasonal levels, meaning the level which is expected in between flu seasons.

In Week 13, around one per cent of visits to health-care professionals were due to “influenza-like illness,” according to the latest FluWatch, which is “slightly below expected levels for this time of year.”

More than 9,500 participants reported their health levels to FluWatchers in Week 13 to give an indication of the prevalence of certain respiratory symptoms within the populace, regardless of confirmed flu status or not. Out of this sample, 1.5 per cent reported cough and fever, a percentage that is below seasonal levels.

Since Aug. 22 and up to April 1, there have been 67,806 influenza detections, 97 per cent of which have been influenza A. In the same time period, there has also been 4,008 influenza-associated hospitalizations reported by participating provinces and territories. Of these, 99 per cent were influenza A cases.