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COVID Modelling

COVID-19 modelling expert says doubling-trend of cases poses risk if continued into fall

Sep 8, 2020 | 12:20 PM

PRINCE GEORGE – Dr. Caroline Colijn admits we’re in one of those moments where she wishes she had been wrong.

Back in the middle of July, the Canada 150 Research Chair in Mathematics for Evolution, Infection and Public Health at Simon Fraser University stated that the province was beginning the see the early signs of renewed growth when it came to new test-positive cases of COVID-19.

“Case numbers were really low province-wide; 10-12 reported cases one day, and then nine, and then 10-12. It was sort of hovering around the re-newed signs of growth and we were saying ‘oh, you know if this continues then, of course, there’s a doubling time before cases double again.’ Unfortunately, that is where we ended up,” said Colijn.

Here in Northern Health, the pattern of new cases mirrors that of the entire province according to Colijn. She says that we’re seeing the travel of people being reflected in the increase in case totals across the province, including Northern Health. As of September 4, Northern Health had experienced 174 cases of COVID-19. Back in July, the health authority went over a month without a single case being reported. There were 65 total cases in Northern Health back on July 13th.

“We realize that we’re not detecting all of the cases. Maybe we’re detecting 10 per cent or 30 per cent, but it’s not 95 per cent. There will maybe be five to ten times more than what’s being reported, and that means we don’t necessarily know where those cases are. Because viruses go where people go, it means there’s still some small baseline risk in the North that as far as the numbers look it reflects broadly the risk that many other areas of the province are facing.”

She states that its been mainly community transmission that has been renewed as case totals across the province have gone up, put our curve back into an upward trend. As a result, she believes the province is continuing the trend of experiencing a doubling of numbers.

“The last few days, there’s been more noise with the reported cases across the province. It’s really looking very up and down, and that makes it very hards to estimate the doubling times. I think we are still sitting at a doubling time between 15-20 days, and we have been for quite a while and it’s been, unfortunately, quite consistent.”

Colijn believes that thinking of the current situation as “doubling time” in terms of case counts is a good way to think of exponential growth.

“To say that it’s a rate or it’s an exponential growth but it’s ten cases, people often think 10, 20, 30, 40. They don’t think 10, 20, 40, 80, 160. That’s really what this is and fundamentally that’s because in an infectious disease cases cause other cases.”

The province is more than capable of handling the hundreds of new cases that have been announced each day as of late according to Colijn, however, she admits the risk is in the growth of cases rather than the current number.

Colijn says it’s important that people realize that the transmission of COVID-19 has made its way into communities and is no longer contained to just long-term care homes. She says the messages of keeping bubbles small and refraining from going to large indoor gatherings of any kind is especially important to limit transmission and bend the provincial curve back down to where rates were back in April and May.

“Every jurisdiction in the world is looking for a sustainable way forward through this pandemic that is not a complete lockdown because we know we did a lot of damage with that lockdown. What we don’t want though is pushing that whole pandemic into the fall. The fall, of course, we can’t spend as much time outdoors like we did in the summer.”