Cold and flu season: What can Canadians expect this year?
In Canada, flu season typically runs from November to April, and while anyone can catch the flu, the virus can sometimes lead to severe complications — even death, which is why experts stress the importance of the annual flu shot.
As temperatures begin to fall, more Canadians are moving indoors, and with that comes the familiar onset of cold and flu season. In Canada, flu season typically lasts from November to April, and while the flu is common, it can lead to severe complications or even death. This is why experts emphasize the importance of getting the annual flu shot.
Several provinces are preparing to roll out this year’s flu vaccine over the coming weeks, starting with vulnerable groups before expanding to the general public. The dominant strain expected this year is influenza H3N2, with some circulation of H1N1 and influenza B, though not in high amounts, according to Gerald Evans, an infectious disease expert at Queen's University in Kingston, Ontario.
"We have a lot of data from South America, Australia, and New Zealand indicating it’s an H3N2 year," Evans said, explaining that the Southern Hemisphere often provides clues about what to expect in Canada. H3N2 is a strain of influenza A, known for causing more severe illness, especially in older adults, young children, and those with weakened immune systems.
Beyond the flu, Canadians should also be aware of other respiratory illnesses that tend to rise during fall and winter, including rhinovirus (the common cold), respiratory syncytial virus (RSV), and COVID-19.
What to Expect This Flu Season
Based on trends observed in the Southern Hemisphere, Evans anticipates this flu season in Canada will be “average.” In countries like Australia, the flu season occurred as usual from May to September, peaking in June and July, suggesting Canada might see a flu case peak in late December and January.
"We expect a typical season starting in late December and early January, although it could extend into February or March, and sometimes there are second waves," Evans said. However, the timing can be influenced by travel patterns, which could introduce the virus earlier.
Kevin Chan, a pediatric emergency doctor based in London, Ontario, noted that illnesses like RSV usually begin in late October or early November and can spike rapidly. Chan also highlighted an interesting trend observed in Australia, where contracting one virus made individuals more prone to catching another.
The Role of COVID-19
Although influenza caused some illnesses and deaths in the Southern Hemisphere, Evans noted that the numbers remained average. However, the impact of COVID-19 was more significant, accounting for the majority of severe cases, hospitalizations, and deaths, particularly in Australia. Evans warned that Canadians should expect a similar trend, with COVID-19 likely to increase as colder weather brings more people indoors.
The availability of updated COVID-19 vaccines by the end of September could help lessen its impact during the winter months, he added.
Importance of Vaccination
The Public Health Agency of Canada (PHAC) stresses that the best protection against respiratory illnesses is vaccination. Flu, RSV, and COVID-19 vaccines are available, though their availability may vary based on age and location. The flu shot is recommended for anyone six months of age and older and typically protects against three or four strains of the flu virus each season.
Getting vaccinated helps reduce the severity of illness, lowers the chances of spreading the virus, and eases the burden on the healthcare system during respiratory season. “The flu shot can make a significant difference, particularly for high-risk individuals such as the very young, the elderly, and those with underlying conditions,” Evans said.
He added that while the flu and COVID-19 are caused by different viruses, meaning the flu shot won’t protect against COVID-19, vaccination remains essential for both.
For COVID-19, the National Advisory Committee on Immunization (NACI) recommends the updated vaccines for both previously vaccinated and unvaccinated individuals at higher risk. Two new mRNA vaccines targeting the KP.2 strain are authorized for use in fall 2024, with Moderna’s SpikeVAX available for those six months and older and Pfizer’s Comirnaty for those aged 12 and older. However, the availability date for these vaccines has not yet been announced.
Regarding RSV, vaccines are now available for older adults and pregnant individuals. Depending on the province, families with infants and high-risk children under two years old may access publicly funded RSV vaccines. This fall, Ontario, Quebec, and Nunavut will offer the monoclonal antibody nirsevimab to all babies going through their first RSV season.
Chan emphasized the importance of timely vaccination: “If we can roll out vaccines by the beginning of October, we should prevent a significant portion of respiratory diseases from overwhelming our hospitals."
In addition to vaccines, Evans reiterated the importance of basic hygiene, particularly regular hand washing. "It’s a simple and effective way to reduce your risk of infection," he said.
