Updated COVID-19 modelling data shows impact of public health measures

How closely recent restrictions are followed will have a large impact on how hard Saskatchewan is hit, chief medical health officer says

SCREEN CAPTURE Saskatchewan’s chief medical officer Dr. Saqib Shahab speaks during a press conference last year.

Saskatchewan is at a crossroads, and how hard the province is hit by COVID-19 in the next few weeks depends strongly on actions taken now.

That was the main takeaway from Thursday’s press conference where Chief Medical Health Officer Dr. Saqib Shahab presented modelling data projecting a handful of possible scenarios, from the best case to the worse, of where Saskatchewan is headed given its current spread of the novel coronavirus.

Shahab presented the four scenarios, broken down by how closely residents follow public health orders and recommendations. The best-case scenario would see at least 60 per cent of residents adopt mask use as part of their regular routine — though Shahab would like to see that number hit 90.

It also projects just 20 per cent of residents taking part in weekly private gatherings, with no more than four other people.

The optimistic scenario also assumes that all age groups follow the guidelines similarly, and half of residents begin working from home. It also includes ¼ historic restaurant/bar attendance and only weekly grocery store visits.

Two estimates of the province’s “Current state” were provided.

One assumes just 30 per cent mask use and weekly social gatherings of ten people. It assumes just 20 per cent of residents work from home, half attendance at bars and restaurants and two grocery trips a week.

The difference between the two scenarios is who adopts more careful measures. Under the more optimistic current state of affairs, people over 60 are more cautious, with only 17.5 per cent taking place in weekly private gatherings, while 35 per cent of the rest of the population continues meeting with friends.

The more pessimistic current state estimation sees all ages behaving similarly, and that 35 per cent mark applies to all age groups.

Then, there’s the pessimistic assumption. Under that model, just 20 per cent of residents wear masks, half still engage in private weekly gatherings and those gatherings include 20 people. Meanwhile, the pessimistic model assumes, only ten per cent work from home and there is no change in bar and restaurant attendance.

The differences between the projections between those four scenarios is striking.

Under the best case, or optimistic scenario, Saskatchewan sees its new cases per day top out at 76, and its six-month cumulative total only reaches 4,830 cases. Only five people would be admitted to the hospital per day, with only a handful requiring a ventilator or trip to the ICU.

A six-month death count in that scenario would be 34.

The optimistic model, though, assumes less spread of COVID-19 than the province is experiencing now. The models that estimate the current state of affairs has much more dire outcomes.

Under the scenario where older populations take more precautions, the province tops out at 3,970 cases per day, with a six month total of 304,000 cases.

That scenario would see 261 people heading to the hospital each day, with a peak of 78 daily ICU admissions, and 469 people requiring a ventilator at one time. Under that trajectory, 2,140 residents would lose their lives.

The other “current state” scenario estimate, where all ages behave similarly, is worse. Under that model, daily cases max out at 5,020, and the six-month case count at 341,000. If this trajectory were to continue, 400 people would be headed to hospital each day, with 132 needing ICU care. At its worst, this scenario would see as many as 808 people in the ICU at any one time, and 3,190 would succumb to COVID-19.

That, though, is still better than the pessimistic scenario, where gathering sizes continue to exceed provincial guidelines and few wear a mask. Under that projection, daily case counts would exceed 8,000. A six-month case count would exceed 400,000, over 1,300 people would be in the ICU at one time and 4,800 people could die.

That’s the scenario, Shahab said, the province is trying to avoid.

Those four scenarios weren’t the only numbers presented Thursday. Shehab also compared the pandemic curve so far across each of the province’s six regions, as well as its reproduction number.

The regional case count charts show what the province has been saying — that earlier on in the pandemic, outbreaks were regional, but for the first time, Saskatchewan is seeing province-wide COVID-19 spread.

The visualization also showed the reproduction numbers in the orange and red zones, far above the target of one or zero. That means that each person who acquires COVID-19 is, on average, infecting more than one other person, contributing to the increasing spread.

“If we did nothing, the reproductive number would be four or five,” Shahab said.

“We have to get that under one. Every little bit helps.”

He said those four scenarios — which improve drastically as more people adopt public health measures — show how much those little things such as mask-wearing, social distancing and staying home when sick, help.

“All these measures help bring the reproductive number down,” Shahab said.

“What it shows is that you can, through fairly simple measures, bend the curve.”

It also shows that the more people who abide by public health measures, the more the curve flattens.

“It’s not just up to a few of us,” Shahab said.

“The higher we go, the longer it takes to bend the curve and the more interventions need to take place. It really is up to all of us.”

The goal, he said, is to get back to where the province was, at either a slow burn or a situation where there are localized issues but manageable peaks and valleys. What the province is seeing now, he said, is more like the dangerous uncontrolled spread, which overwhelms the health care system and results in more dire consequences.

The most recent measures, which limit household gatherings to five, mandate mask-wearing in public when indoors and encourage people to work from home and only go out if absolutely necessary, will take a week or two to have an effect.  If people follow the guidelines, Saskatchewan will return to the optimistic forecast and outcomes will improve.

However, it will get worse before it gets better. Shahab explained that hospitalizations follow viral spread by a few weeks. He said the hospitalization rate has been following the modelling scenarios outlined Thursday, and that the hospitalizations and deaths from the current spike in cases won’t be felt for another few weeks.

If cases come down, though, those numbers will then follow.

Shahab will be watching closely.

“The next two to three weeks we have to be extremely cautious. If our curve trends down and we come to less than 60 cases per day, we can start relaxing,” he said.

“Right now, modelling, epidemiology and tracking where we go is really important. If it doesn’t bend down, we will have to think about other measures.”