A new strain of H3N2 influenza is landing a growing number of Canadians in hospital with cases “increasing rapidly” around the country.
All indicators of influenza activity are increasing quickly, with all regions throughout the country reporting growing influenza activity, Health Canada said.
In the first week of December alone, Canada saw 6,799 cases of the flu detected, with 91 outbreaks across the country. The number of positive tests rose 20.2 per cent compared with the week before.
More Canadians landed in hospital that week, with 3.6 hospitalizations per 100,000 of population.
The dominant strain being observed in Canada and the United States is the influenza A(H3N2) strain, including a subvariant — A(H3N2) subclade K — the World Health Organization said.
Children are among those being hit hard, with most infections being detected in people under 19, according to Health Canada.
In Ottawa, three children between the ages of five and nine have died from influenza A-related complications, with the city’s health officials urging anyone over the age of six months to get vaccinated.
In November, the Children’s Hospital of Eastern Ontario saw eight times more children test positive for influenza compared with the same month last year and double the number of children who needed to be hospitalized with the flu.
“The flu is more than a bad cold,” the hospital, colloquially known as CHEO, said in a statement.
“Children under five are at a higher risk of severe illness from influenza because they have smaller airways, and their immune systems are still developing. Even healthy kids can become seriously ill, and flu spreads quickly in schools and child-care settings.”
In Alberta, hospital emergency rooms are seeing a flood of influenza patients as cases in the province have jumped 70 per cent in a week.
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“Now one in five of all tests that are being done are positive. So that suggests we’re right in the midst of that surge. That number could go higher,” said Dr. Fahad Razak, internal medicine physician and professor at the University of Toronto.
The surge comes as Canadians are looking to travel to be with family and loved ones for the holidays.
“It’s probably going to end up being a more severe and a more significant flu season compared to the average flu season,” said Dr. Isaac Bogoch, infectious disease specialist at Toronto General Hospital.
Canada will likely see more hospitalizations and more pressure on the health-care system, Bogoch added.
The dominant strain of the virus is causing cases to rise in other parts of the Northern Hemisphere as well.
In the U.K., the National Health Service said it is currently facing a “worst case scenario” situation for December as flu hospitalizations have surged by more than half in just one week.
An average of 2,660 patients per day were in a hospital bed with flu last week – the highest ever for this time of year and up 55 per cent compared with the week before, the NHS said in a statement last week.
In the U.S., influenza infections are growing or likely growing in 43 states, according to the U.S. Centers for Disease Control.
The mutation of the virus is a normal phenomenon, Bogoch said.
“You have to pick the appropriate vaccine based on the circulating strain of influenza months in advance so that there’s enough time to mass-produce and then distribute these vaccines. Unfortunately, this virus is prone to mutation, and it mutates every year and we have to constantly update the vaccines,” Bogoch said.
Most years, vaccine makers get it mostly right, he said.
This year, however, the particular strain has proven trickier than usual.
“This year, the vaccine still works. It just doesn’t work as well as we would like for the H3N2 component,” he said.
Subclade K is “enhancing the ability of the virus to slip through some of our immune protections,” Razak said. However, both experts said being vaccinated against the flu could help protect you from the worst effects of the virus.
“If you look at deaths and severe illness with flu, the vast majority both in adults and in children are unvaccinated,” Razak said.
“Yes, you may get sick, even if you are vaccinated, it’s that the severity, the chance that you’re going to end up in hospital and worst-case scenario in the ICU or die does seem to be significantly protected against by being vaccinated.”
Vaccinations can prevent anyone infected with influenza from developing further complications, Health Canada said.
“Staying up to date with recommended vaccines is one of the most important ways to protect yourself from developing serious complications from respiratory illnesses such as seasonal influenza (the flu), COVID-19 and respiratory syncytial virus (RSV). Talk to your health care provider or local public health about vaccines that are recommended for you,” a Health Canada spokesperson said.
The agency also recommends staying home when sick and wearing a well-fitting respirator or mask in crowded and closed settings.
Mask-wearing is also recommended for anyone who has more serious complications from a respiratory infection, or spends a lot of time with others who are at risk, such as older people, young children, pregnant women and individuals and people with weakened immune systems, Health Canada said.
Cleaning your hands regularly, covering coughs and sneezes and cleaning and disinfecting high-touch surfaces and objects can also help, the agency said.