Compliance key variable in updated COVID-19 modelling

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This article was published 04/12/2020 (1689 days ago), so information in it may no longer be current.

Manitoba’s top doctor and nurse presented updated COVID-19 modelling Friday for the first time in seven months.

The charts and graphs show November’s code red restrictions were needed in part because the public didn’t take October’s code orange restrictions seriously enough.

Dr. Brent Roussin, chief provincial public health officer, and Lanette Siragusa, chief nursing officer for Shared Health, stressed Manitobans determine the effectiveness and duration of public health restrictions.

Four scenarios

The province used “agent-based” modelling to simulate the lives and decisions of Manitoba residents to show how the spread of the coronavirus changes as restrictions and public compliance increase or decrease, the province said in a release.

Roussin and Siragusa detailed four possible COVID-19 scenarios used to simulate projections that extend to Dec. 31. Roussin said agent-based modelling tends to become vague beyond a few weeks into the future.

The four scenarios are “extreme” (minimal restrictions and poor compliance with public health recommendations), “severe” (some restrictions and poor compliance), “moderate” (more restrictions and good compliance), and “controlled” (full restrictions and good compliance).

Notably, only the moderate and controlled scenarios result in a level of virus activity low enough to be manageable for the province’s health-care system.

Roussin said limited vaccine availability early next year won’t bring down total case numbers immediately, but will reduce the number of hospitalizations and deaths by protecting the most vulnerable citizens.

Case numbers

The figures released Friday suggest Manitoba has yet to reap many benefits from the code red restrictions imposed Nov. 12. The measures are set to expire Dec. 11 but Roussin is widely expected to extend them.

“Test positivity rates remain high, and for that reason it is too early to say we are changing trajectory,” Roussin said.

Manitoba’s case numbers have followed the extreme scenario in recent months. The current number of daily diagnosed cases put Manitoba in the low end of the extreme scenario.

“We are not out of the woods yet and must remain vigilant to prevent another spike,” Roussin cautioned.

On average, every 48 cases of COVID-19 in Manitoba produces three hospitalizations and one death.

Of the more than 357,000 tests for COVID-19 processed between March and November, 4.78 percent came back positive. For every case confirmed with a positive test result, Roussin said it’s likely there are five to 10 more cases circulating undetected.

Death projections were omitted from the presentation. Roussin said coronavirus fatality is around two percent, making mortality predictable, but stressed models are not “a crystal ball.”

First wave vs. second wave

Roussin said first-wave cases were predominantly linked to travel, while community transmission is powering the second wave.

He underscored the severity of the second wave, noting lately, daily new cases are exceeding the total number of cases seen during the entirety of the first wave.

To date, 362 Manitobans have died from COVID-19, but just 21 died before Sept. 30.

Similarly, only one Manitoba long-term care home had an outbreak as of July 30. Thirteen outbreaks occurred in August and September, rising to 51 in October and November.

Manitobans in their 20s comprised the largest portion of cases since the pandemic began. By fall, those in their 30s and 40s made up the greatest percentage of cases.

“The second wave started largely in the younger adults,” Roussin said.

It’s an age group that tends to be active in the community, he explained.

“This is a group that makes up a large part of our workforce. They keep our services going and goods flowing.”

Roussin dispelled the notion that younger people don’t have to worry about COVID-19. To date, the virus has hospitalized 29 people under the age of 20 and killed 23 Manitobans who were in their 40s or 50s.

“It’s taking younger adults from us all too soon,” Roussin said.

Cases in children are on the rise and make up 18 percent of total cases.

The infection curve for those under age 20 began rising almost as soon as schools reopened. Roussin attributed that to community transmission.

The modelling suggest in-school transmission remains rare, with six of Manitoba’s 802 public and independent schools showing evidence of in-school transmission. A further six had outbreaks of more than five cases.

Hospital capacity

COVID-19 has hospitalized nearly 1,100 Manitobans through November. Manitoba has added 627 hospital beds and 101 ICU beds since the pandemic started.

While hospital activity related to COVID-19 remains high, Siragusa said restrictions are helping to avoid a “catastrophic impact” that would affect all Manitobans needing any type of care.

Modelling showed the province could have exceeded its ICU capacity as soon as Nov. 23 were it not for public health restrictions.

“We’ve dodged a crisis,” Siragusa said.

Modelling showed hospital admissions are in the upper end of the Severe scenario. New daily hospital admissions are hovering in the middle of the Moderate scenario. Hospital occupancy is tracking in the middle of the Severe scenario.

ICU admissions are in the middle of the Moderate scenario, with COVID patients expected to occupy half the province’s ICU beds by the end of the year.

“Even in the current trajectory, case counts are still too high for our health system to be able to support,” Siragusa said.

She dwelled on the widespread redeployment of health-care staff to COVID units, and the challenge of maintaining care for other types of patients.

“Our health system must care for all Manitobans in need of health services, not just those with COVID-19,” Siragusa said.

She explained staff, not equipment, are the health-care system’s most valuable resource as the pandemic wears on.

“Our vulnerability…is that of staff, who they themselves are at risk of fatigue, illness, or exposure as they fight this virus,” Siragusa said.

Responding to questions following their presentation, Roussin said the models don’t indicate whether the province should have locked down sooner.

Manitoba’s case numbers entered the extreme range in early October. Roussin acknowledged “the benefit of hindsight” and explained the province wanted to try a “targeted approach” with the second wave before resorting to code red restrictions.

“You could see we didn’t get the buy-in from (code orange restrictions),” he said.

Roussin attributed the low public compliance in October to fatigue.

“We’ve been at this for nine months and I think that Manitobans, just like probably everyone else in the world, want to be done with this virus and done with these restrictions. But unfortunately we’re not. And our modelling shows what will happen if we loosen up on this.”

The Manitoba government last released detailed modelling data in late April.

At that time, Roussin predicted Manitoba could see 6,250 cases by the end of the year. Instead, the province has already surpassed 18,000 cases.

Manitoba currently has 9,172 active cases of COVID-19.

A total of 320 new cases were announced today, 54 of them in Southern Health.

Two of nine deaths announced today were also in Southern Health: a man in his 70s and a woman in her 80s.

“We’re losing too many Manitobans, so we need to stay home (and) reduce our number of contacts,” Roussin said.