COVID-19 spreads easier in winter, but not clear why that is

Seasonality of COVID-19

The transmission of COVID-19 in B.C., and across the country, has risen sharply in recent weeks, partly due to the virus spreading easier in the winter. But it's not clear why that's the case.

On Friday, the number of new COVID-19 cases identified in the past 24 hours hit a record high, with 911 new cases and 11 new COVID-related deaths.

“What we are seeing is that this time of year, for reasons that we don't entirely understand, some viruses spread more easily between people,” Dr. Bonnie Henry said Friday. “We see that with influenza .. and we've seen it with other coronaviruses which cause much more milder illnesses.

“So there is a seasonality to this virus that we're just learning, so that means as we move into winter, not only are we indoors more and having more contact with people indoors, but also the virus is spread much more easily. So it is a combination of things.”

B.C. has had more 5,410 new cases identified in the past week alone, along with 64 deaths. Dr. Henry said countries around the world are seeing similar seasonal spikes.

“We seemed to be holding our own and then it was almost like a switch where we started to get rapid increase in cases,” she said. “It's the same in Europe, it's the same across Canada and in the United States.”

Dr. Henry noted the rapid spread is not related to any mutation of the virus, as the COVID-19 virus appears to mutate quite slowly.

“[This] speaks to the fact that a vaccine is likely to be more effective and we've seen some results of that,” she said.

But due to the increased transmission, some of the things that were relatively safe in the spring and summer, and even a few weeks ago, have become more risky.

“Those guidelines that we had, those COVID safety plans that worked fine up until a few weeks ago, we now need to step back and say there's some things that are just too risky given this climate that we're in right now,” Dr. Henry said, noting the additional public health orders that have been in place to try and slow the rapid transmission of the virus.

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