Why so many people in Canada seem to be sick right now
Influenza widespread in many parts of the country, Public Health Agency of Canada says
You may be seeing and hearing a lot of people coughing and sneezing around you right now.
Why? Well, Canada's winter respiratory virus season got off a late start and now it is in full swing, officials say. That suggests more people are sick with the flu and landing in the hospital compared to years past.
"We haven't seen this amount of influenza cases as well as severe illness in almost a decade," said Dr. Karim Ali, medical director for infection prevention and control and head of services for infectious diseases at Niagara Health in Ontario.
In Quebec, Dr. Jesse Papenburg, an infectious disease specialist at Montreal Children's Hospital and an associate professor of pediatrics at McGill University, says about one out of every three tests sent for influenza in the province currently comes back positive for flu, which reflects the intensity of this flu season.
"I think this is influenza doing what influenza does, striking in the middle of winter with an intense epidemic," said Papenburg.
For several years up until 2023, he says about 10 to 20 per cent of children admitted to pediatric hospitals for influenza needed intensive care. Back in 2006, Canadian researchers reported about 12 per cent of children hospitalized with influenza were admitted to intensive care. This season's data isn't yet broken down.
Papenburg also notes that the flu vaccine helps protect children from being infected. "My recommendations for families is, it's not too late to get vaccinated."
On Friday, the Public Health Agency of Canada noted flu activity was "widespread" in British Columbia, Ontario and Quebec. COVID-19 and respiratory syncytial virus (RSV) were decreasing, PHAC said. In Canada, flu season typically lasts from November to April.
Later peak, more illness?
Dawn Bowdish, a professor of medicine at Hamilton's McMaster University, pointed to national goals of vaccinating 80 per cent of vulnerable people, such as the youngest and oldest. The influenza vaccine uptake goal is meant to protect those at high risk of infection and complications from the respiratory illness, according to the Public Health Agency of Canada.
Bowdish, the executive director of the Firestone Institute for Respiratory Health, says Canada has never hit that target. "The good news is that in people over 65, we're starting to creep up over 70 per cent," she said.
Influenza vaccines are also important during pregnancy, she noted, to prevent bad outcomes for both the pregnancy and the woman's health, as well as to pass on protection from the mother to baby to keep newborns out of the hospital
Other priority groups for flu shots include those who have asthma, people with heart conditions, people who are immunocompromised and anyone planning to receive chemotherapy for cancer.
Bowdish says that as with COVID-19 vaccinations, waning immunity from fall flu shots could be playing a role now.
"When the peak comes later, like February, most people are past that three months of protection, which could explain why we're seeing so many admissions this year," she said.
Nationally, influenza vaccination coverage in 2023-2024 was 42 per cent, about the same as the previous season. The findings were published in December by the Public Health Agency of Canada.
Watch for transition season
Dr. Danuta Skowronski heads up epidemiology for influenza at BC Centre for Disease Control and leads an annual study into influenza vaccine effectiveness.
Skowronski says her team has found that the vaccine reduces the risk of flu illnesses that require a medical visit "by about half" through mid-January.
Her team's findings based on data from British Columbia, Alberta, Ontario and Quebec as well as the National Microbiology Laboratory, were published Jan. 30 in the medical journal Eurosurveillance.
Skowronski says, a mix of two Influenza A subtypes, H1 and H3, are circulating this season.
"Last year, it was predominantly an H1 season for us, so to see a second season in a row of H1 is a little unusual," she said. "But to have both H1 and H3 suggests to me that this may be a transition season and we should be watching for emergence of a kind of a dominant variant that may take off."
On top of vaccination, Skowronski suggested people layer various precautions to avoid infection and illness. For instance, if a grandchild has a flu-like illness then it may be best to avoid visiting. Or a person at high-risk of complications may want to consider getting a prescription for an antiviral medication early on in their illness.
She says her team will continue to monitor flu vaccine effectiveness closely over the rest of the season because a small proportion of viruses tested showed variants that may influence deliberations about the composition of influenza vaccines for the Northern Hemisphere at the World Health Organization's meeting in London later this month.
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With files from CBC's Alison Northcott, Melanie Glanz and Jennifer Yoon