Alberta may face a particularly severe flu season this fall, along with a potential further increase in COVID-19 cases, causing concern for some doctors.

Infectious disease experts often look at trends in the Southern Hemisphere to predict what the Canadian flu season will be like. So far, Australia is experiencing a severe wave of respiratory illnesses.

The flu season in Australia started early, and the number of lab-confirmed cases was higher than the five-year average.

Dr. Dan Gregson, an infectious disease physician and medical microbiologist and assistant professor at the University of Calgary's Faculty of Medicine in Cumming, said, "The concern is that we will face what we call a 'bad flu season,' which results in many hospital admissions for treatment. Additionally, we have cases that will coincide with COVID at the same time."

He added, "If COVID admissions rise at the same time that flu outbreaks are higher than usual, the pressure on hospitals will be high once again."

Alberta did not report any flu cases during the 2020-21 season.

However, with the lifting of pandemic-related public health measures, Alberta has seen the return of respiratory viruses and an unusually delayed flu season this year.

Dr. Stephanie Smith, an infectious disease physician at the University of Alberta Hospital, explained, "This is due to a phenomenon known as immune debt."

"Basically, we have not been exposed to many of these viruses for nearly two years now. So our bodies took a short break and were suddenly exposed to this amount of viruses without really having this kind of additional protection. Therefore, people will be more susceptible to a variety of infections."

All this comes at a time when Alberta hospitals are under severe pressure due to a number of factors, including staff shortages.

Dr. Stephen Friedman, a professor of pediatrics at the University of Calgary and an emergency physician at Alberta Children's Hospital, said, "I am more focused on where we are right now."

"Emergency departments currently in Alberta and across Canada, especially pediatric emergency departments, are extremely busy, and we are doing our best to handle the volume and severity of illness we are currently seeing."

While Friedman is still treating many children for COVID-19, respiratory syncytial virus (RSV), and flu, he said that numbers are declining and hopes to see a further decrease in viral illnesses in the coming weeks.

Friedman also said, "I think we will probably start seeing that here just as some of those other viruses decline. And then at some point, we are likely to see an increase in flu cases similar to what we see in Australia."

"It is just a matter of timing and how these things overlap that will determine the severity of the upcoming viral respiratory season we will experience."

In an effort to protect the healthcare system this fall, Gregson said a number of key steps must be taken, including government messaging that masks may be required if hospitals are at risk of overcrowding.

He said, "The best we can do is prepare for that."

Editing: Dima Abu Khair