Alberta has been working on COVID-19 models since January and just released them to the public on Wednesday.

The models contain several scenarios, including one labelled "probable," which had forecast roughly 200 people would be in hospital with the disease by April 8. In reality, there were fewer than 50 patients hospitalized by then.

The rate of hospitalization in Alberta is also significantly lower than in Quebec, Ontario and British Columbia. The rate of people in ICU is even lower.

All this leads to the question: Why?

The answer is: We don't yet know, for sure. But there are some ideas.

Premier Jason Kenney has cited several possible reasons, including the province's testing and contact-tracing protocols, the age of its population and the geographic distribution of its citizens.

Scientific experts were less willing to point to a specific reason, saying more data is needed before drawing firm conclusions about what's happening with COVID-19 in the province. They caution, too, that the outbreak is still in relatively early days and things could change. But if the low hospitalization rates do keep up, the modellers say the forecasts for Alberta could change, too — for the better.

For most Albertans, though, the arcane details of epidemiological forecasts are less striking than the latest numbers.

Here's what those look like.

Patients in hospital and ICU

At last count there were 44 people in hospital in Alberta with COVID-19, including 16 in intensive-care units.

In B.C., which has slightly fewer confirmed cases and a slightly larger population, there were 135 hospitalized patients, of which 61 were in ICU.

But the biggest differences are seen when you compare Alberta to Ontario and especially Quebec, where hospitalizations have risen dramatically in the past couple of weeks. At last count, the number of patients in hospital had surpassed 600 in both provinces.

Of course, Ontario and Quebec have larger populations than Alberta. But even on a per-capita basis, the differences are stark, which you can see in the chart below.

A key thing to keep in mind when looking at these numbers, however, is when the COVID-19 outbreaks started in Alberta relative to other provinces.

"We're about two or three weeks behind," said Geneviève Kerkerian, an infectious disease fellow at the University of Calgary.

So while Ontario and B.C. had each confirmed a handful of cases by early February, Alberta didn't record its first case until March 5.

Quebec didn't see its first case until Feb. 27 — just over a week before Alberta's — but experts have pointed to the unfortunate timing of that province's earlier spring break, which brought many travellers home from international destinations just before major social-distancing measures went into effect.

Will Alberta follow the same paths as these other provinces, just a few weeks later?

Kenney said there's reason to think it won't.

What's different about Alberta

The premier acknowledged the earlier outbreaks in places like Ontario and B.C., but said Alberta's later start actually gave it a head start in taking countermeasures against the disease.

Testing, in particular, ramped up early on in Alberta. For some time, the province led both Ontario and Quebec in the total number of tests completed, despite being so much smaller in population. It still leads all provinces in testing per capita.

"Because of our stronger testing, we also have been ahead of the curve in Canada on tracing and containment," Kenney said.

Another possible factor?

"We have the youngest population in Canada," the premier said. "And that counts for a lot in a disease like this, which attacks the elderly much more aggressively."

And finally, Kenney said, Albertans are "much more spread out" than people living in other large provinces, which have more concentrated populations in larger urban centres.

"Obviously, we have two urban metropolises, but it's still a big province," he said.

"People who might come into contact with COVID-19 multiple times — let's say they are working in a hospital or live in a very densely populated downtown urban area — chances are that if they get infected, it might be multiple times or it might be with a more powerful load of virus than perhaps somebody living in the country."

So what about those models?

Modellers always looking for new data

Kenney presented the bottom-line results of Alberta's COVID-19 models on Tuesday night, in a televised address.

The details were released Wednesday, when several of the experts involved in creating the models also provided reporters with a technical briefing on how they were made.

They acknowledged the actual hospitalization numbers that we've seen to date are "significantly lower" than what was forecast for early April, even in the "probable" scenario and especially in the "elevated" scenario, where the disease spreads wider and faster.

By April 8 in the 'probable' scenario, Alberta's models forecast roughly 200 people would be in hospital with COVID-19. In reality, there were fewer than 50. (Alberta Health; annotation in red by CBC)

But the modellers also cautioned that, while it might feel like COVID-19 has been dragging on for some time, it remains "very, very, early days" in terms of predicting where the disease will go.

That said, it's better to be below the forecast for hospitalizations than above it, and the experts said they are always looking at the latest data and will adjust the models if and when the evidence demands it.

Still 'too soon' to say for sure

As a clinician, Kerkerian said she's not involved in the modelling side of things, but says observations of the virus's behaviour suggest it's still "too soon" to say whether Alberta's hospitalizations will stay low or follow a similar rise as has been seen in other provinces.

It can take up to 14 days for a person infected with the novel coronavirus to start showing symptoms, she noted. From there, it can take another seven to 10 days for people to end up in hospital.

The province's data also shows a greater proportion of confirmed cases among older people in the past couple of weeks than in the weeks prior to that.

This, to a large extent, is related to changes in testing criteria on March 23 which placed a higher priority on older people and those most vulnerable to the disease.

But Kerkerian said the possibility of recent infections among vulnerable populations showing up sometime down the road in hospital "is definitely something we are taking into consideration"

"We're estimating a lot of people that were infected in the past few weeks or are currently being infected will probably require a higher level of care — so hospital admission or ICU admission — in the next few weeks," she said.

Kenney, for all his optimism, also sounded a cautious note.

"For a number of reasons, we are experiencing — so far — less severity," he said. "But again, that's something we cannot take for granted."

Deena Hinshaw, Alberta's chief medical officer of health, said the path Alberta takes will ultimately depend on Albertans.

"The most important factor in how big or small the impact of COVID-19 is in the province is the behaviour of each and every one of us," she said.

"This cannot be stressed enough. If Albertans stop following public health restrictions and guidelines, we can expect to experience a higher impact than the data currently suggests. If Albertans strictly follow all public health guidance, we collectively can further reduce the impact from what the modelling is currently predicting."