B.C. health officials haven't found a single case of seasonal flu spreading in the community this winter

Health officials in B.C. have not detected a single case of influenza circulating in the community since flu season began, continuing an"exceptional" nationwide trend even as the province sits in thethick of its regular flu season.

The B.C. Centre of Disease Control (BCCDC) confirmed the non-existent seasonal flu numbers to CBC News on Monday.

"It's still a big goose egg in terms of influenza detection provincially. It's really quite exceptionalhow low the influenza activity is," said Dr. Danuta Skowronski, the lead for influenza and emerging respiratoryvirus monitoring at the BCCDC.

"I've been on the influenza beat for 20 years and I've never seen anythinglike this ... and that's not for lack of trying."

The BCCDC has tested 30,000 samples for influenza this year. Only a dozenof those tests came back positiveandall were linked to people who'd receiveda vaccine, which doesn't count as community spread.

By comparison, the centre found 861 positive tests last year with roughly one-third of the testing.

B.C.'s experience is reflected across the country. A report from thePublic Health Agency of Canada on Thursday saidthere hasn't been enough influenza cases to even declare that the 2020-21 flu season has begun in Canada.

The statistics have calmed fears of health experts across Canadawho worrieda second wave of COVID-19 would arrive just as seasonal flu infections began to spread,creating an overwhelming "twindemic" this winter.

"We are trying to find that [influenza] virus, but so far, nothing which is good news," said Skowronski.

COVID-19 measures caused 'dramatic drop-off'

The 30,000 tests run for the flu this yearis four times the average number of tests B.C. has done over the past five flu seasons. The dozen positive results were all connectedto people who'd received the"live attenuated" flu vaccine, which ismade from weakened influenza virusanddelivered by nasal spray.

"It's not unusual to pick up the vaccine virus in the nose swab,"Skowronski said. "What is unexpectedis to find no influenza viruses otherwise at all in the province."

Flu season typically peaks in B.C. in December and January. Skowronskisaid public health measures taken to slow COVID-19 like handwashing, physicaldistancing, mask-wearing and reduced travel are likely what's thwarted the regular flu.

"We saw a dramatic drop-off in influenza activity almost as soon as we implemented those public health measures last March. We were experiencing an influenza epidemic then and as soon as those measures were in place, it was like influenza fell off a cliff ... and it's been like that ever since," she said.

Influenza and COVID-19 are both contagious respiratory illnesses, but they are caused by different viruses. The flu comes from influenza viruses, while COVID-19 is caused by a novel coronavirus calledSARS-CoV-2.

As for whether the public health measuresshould remain in place to ease flu season even after COVID-19 is under control,Skowronski said it's an idea for health officials to consider.

"I think it would be useful to take stock of the measures and what's worked, but it's a balance. Some of those measures are quite extreme and are put in place because, ultimately, the SARS-CoV-2 virus is not the influenza virus," she said. "It takes a much greater toll in terms of hospitalizations, ICU admissions and deaths than typical influenza season virus does.

"We'll have to weigh the benefits and the costs of those measures."