Since the flu shot takes 10 to 14 days to become active, Dr. Donald Vinh of the MUHC advises people to go soon so they will be better protected and less likely to spread the disease during the holidays, which often bring together children and the elderly.
Many people still dismiss the flu as little more than a bad cold. Canadian doctors say that assumption can be dangerous. This season’s dominant strain, influenza A H3N2, is spreading quickly and causing unusually severe illness, including deadly complications in children.
The warning comes after the deaths of three children in the Ottawa area from influenza-related complications. Public health officials say the cases highlight how serious the flu can be, especially during a heavy season.
Child deaths raise alarm in Ontario
Ottawa Public Health confirmed that three children, aged between five and nine, died after developing complications linked to influenza A. The deaths occurred as parts of Ontario and Eastern Canada report a sharp rise in flu cases.
Doctors stress that while such outcomes are rare, they are a reminder that influenza is not a mild illness.
Why the flu can turn dangerous
Dr. Christopher Labos, a Montreal-based epidemiologist and cardiologist, says influenza can trigger a chain of serious medical problems.
The virus can lead to severe pneumonia, often complicated by secondary bacterial infections. It can also damage the kidneys and cause renal failure. In older adults, influenza is linked to a rise in heart attacks and other cardiac events.
“These complications are why calling the flu ‘just a cold’ is incredibly problematic,” Labos said. “Influenza is a very severe viral infection.”
A virus that kills worldwide
Dr. Isaac Bogoch, an infectious disease specialist in Toronto, said the flu’s global impact is often underestimated.
Influenza kills an estimated 400,000 to 500,000 people worldwide each year. In Canada alone, between 2,500 and 3,500 people are expected to die from flu-related illness this season.
The virus is most dangerous for young children, older adults, and people with weakened immune systems or underlying health conditions.
What makes this season different
Influenza is not a single virus but a group of constantly evolving strains. Each year, one strain tends to dominate.
This season, H3N2 is responsible for most infections seen across Canada. According to Labos, the strain appears more virulent and is causing more severe disease than usual.
Health experts had early warning signs from the southern hemisphere, where winter flu seasons often predict what northern countries may face months later. What doctors saw there is now being reflected in Canada.
Symptoms to watch closely
Influenza is a respiratory infection, but its effects can extend far beyond a sore throat.
Common symptoms include high fever, cough, shortness of breath, and intense muscle aches. In severe cases, patients may need supplemental oxygen or hospital care.
Doctors urge parents to seek medical attention if a child shows worsening symptoms, breathing difficulty, or extreme fatigue.
Why children are being hit hard
Recent Ontario data shows particularly high infection rates among children aged five to 11.
Labos says biology plays a role, but school environments are a major factor. Children spend hours indoors, often in crowded classrooms with poor ventilation.
“Kids spread viruses to each other very efficiently,” he said. “Unless we invest in better ventilation and air filtration, we will keep seeing outbreaks in schools.”
Vaccination remains the best defence
Health experts agree the flu shot remains the most important protective measure.
This year’s vaccine is not a perfect match for the circulating H3N2 strain. Still, Labos says it provides meaningful protection by reducing severity and lowering the risk of complications.
Bogoch echoed that advice, stressing that it is not too late to get vaccinated.
Everyday steps to reduce spread
Doctors also recommend staying home when sick, washing hands regularly, and wearing masks in high-risk settings like public transit or medical facilities.
These simple measures can help protect vulnerable people and reduce pressure on hospitals.
Flu activity rising sharply
Canada’s latest respiratory virus surveillance report shows influenza positivity jumped to 20.2 per cent in early December. That is up from 13.1 per cent the week before.
At the same time last year, the positivity rate was just 3.1 per cent. Health officials warn that flu activity is rising rapidly.
Hospitalizations, including pediatric admissions, are increasing. Most positive tests are linked to influenza A, especially H3N2.
Doctors say the message is clear. The flu should never be treated lightly.
