Newspaper article The Canadian Press

Flu Case Numbers Spiking across Canada, Heralding Peak of Epidemic: Experts

Newspaper article The Canadian Press

Flu Case Numbers Spiking across Canada, Heralding Peak of Epidemic: Experts

Article excerpt

Flu cases spiking, heralding peak in epidemic

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TORONTO - The number of flu cases is continuing to rise across Canada, suggesting the peak of infections with one of the dominant circulating strains could come within a few weeks -- or even sooner, say infectious diseases experts, who describe this influenza season as "unusual."

"We really haven't seen a season quite like this in a little while," said Dr. Michelle Murti of Public Health Ontario, referring to the mix of two primary strains making people sick during this year's epidemic.

The dominant influenza A strain is H3N2, a nasty virus that tends to infect the elderly in greater numbers, with concurrent circulation of a B strain, a type that typically causes less severe illness. Influenza B can also affect older people and is the strain that most often infects children.

"Normally in a season, we'll see a peak of influenza A happening some time towards the end of December or through January," Murti said Monday. "And as that is coming down toward the end of February, that's when we start to see that peak of influenza B activity into the spring and later season."

But this year's B strain, known as B/Yamagata, began circulating in the fall, much earlier than is usually the case.

British Columbia, for example, is seeing an atypical 50-50 mix of H3N2 and B/Yamagata, although other regions in Canada may have different ratios of the two strains affecting their populations, Dr. Danuta Skowronski of the BC Centre for Disease Control said from Vancouver.

"The spike in influenza activity that we're experiencing now is not unusual," she said. "In fact, such a sharp increase in activity is a signature feature of influenza that distinguishes it from other respiratory viruses that have a more prolonged, grumbling activity through the winter period."

Skowronski described graphs illustrating flu activity as looking like a church steeple -- with a sudden rise, a peak and then a sharp decline.

"We are currently spiking, but whether we have passed the peak or are continuing to rise, it's still too early to tell," she said, adding that peaks may arrive at varying times across the country as regions and communities experience major upticks in cases at different points in the epidemic. …

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