EDMONTON -- The 177 Albertans in intensive care units sick with COVID-19 could grow to 200 or more by the first week of June, officials expect.

At his last news conference on Tuesday, Premier Jason Kenney estimated Alberta's hospitals could be providing critical care to 200 COVID-19 patients before the end of May, plus some 60 Albertans who've suffered heart attacks, vehicle crashes and other medical traumas.

But an Edmonton doctor believes the premier's projection is low.

Dr. Noel Gibney, co-chair of the Edmonton Zone Medical Staff Association's pandemic committee, thinks Alberta will count more than 1,100 COVID-19 hospitalizations and ICU admissions in the low-200s at the crest of the third wave.

"In my view, we've got another three weeks to go before we hit the peak," Gibney told CTV News Edmonton on Thursday.

"As long as we don't get to somewhere around the 300 (ICU) mark, we're not going to be in the so-called red zone."

The "red zone" has been Kenney's way of describing when Alberta runs out of beds to care for ICU patients. Having reduced about 30 per cent of non-urgent surgeries in the Edmonton zone, the province has ICU beds for 425 patients suffering from coronavirus or not.

On Tuesday, there were 169 Albertans with COVID-19 in ICUs, and a total of 737 COVID-19 patients in hospitals.

At the peak of Alberta's second wave in December, total COVID-19 hospitalizations breached 900. The province already has broken its COVID-19 ICU record.

Forecasting is complicated math, Gibney said. Now that nearly 70 per cent of Alberta's population 60 years and up has received at least one dose of vaccine, he noted hospital trends are changing: the average length of stay has gone down because younger people have fewer comorbidities; patients are being hospitalized a longer time after first being infected (two weeks for hospital patients, three weeks for ICU patients).

On the other hand, the province has done about two thirds of the testing it did the week before, but Alberta's positivity rate has been higher than eight per cent for 11 days straight.

If both acute cases and the positivity rate came down, Gibney explained, it would likely mean infection rate is falling, as well.

"But the fact that the positivity rate is still high out there strongly suggests there's a significant number of people who, for whatever reason, simply aren't going for testing."

The premier, too, cautioned against reading into the apparent plateau of daily new infections.

According to Kenney, about 0.78 per cent of recent COVID-19 cases have ended up in ICUs. At that rate, the province's health officials are expecting around 250 COVID-19 ICU patients at the beginning of June.

"We can manage that – with great difficulty," Kenney said Tuesday, telling reporters if COVID-19 ICU patients breached 300, more surgeries would have to be cancelled.

"Let's pray for a miracle. Let's hope that all of a sudden all these new cases… don't end up in hospital – but the science tells us different.”

Given the situation, Gibney stressed the significance of the public continuing to follow public health orders and get vaccinated, which will enable the province to plan for reopening toward the end of June.

"There's always this temptation to open up sooner than is advisable," he commented.

"The answer there would be to make sure the positivity rate is ideally lower than five per cent. And at the same time, make sure the level of new cases is a manageable level."

With files from CTV News Edmonton's Jeremy Thompson