Infectious diseases experts describe this influenza season as “unusual,” in that a mix of two strains are dominating this year’s flu epidemic.
The number of flu cases is continuing to spike across Canada, suggesting the peak of the season could still be a few weeks off, 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 strains dominating this year’s flu 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 seniors 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, said Dr. Danuta Skowronski of the BC Centre for Disease Control.
B.C. is currently seeing about 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, Skowronski said from Vancouver.