It’s relatively calm on Canada’s respiratory virus front heading into the holiday season, but doctors are concerned about additional cases of bird flu being identified in North America and possible viral mutations.
Influenza cases are rising nationally but remain at seasonal levels, according to the Public Health Agency of Canada’s latest FluWatch report, which details influenza trends across the country. Respiratory syncytial virus, or RSV, is also gaining ground while COVID levels are decreasing. Waste-water testing, also from PHAC, found viral levels of COVID and flu are moderate, while RSV is high.
Flu season was irregular after the height of the COVID pandemic – with earlier and more intense presentations of the virus – but is settling back into a more standard pattern, which means there will likely be an uptick of people getting sick into January and February. The current situation this holiday season should come as good news, said Fiona Brinkman, a professor of genomics and bioinformatics at Simon Fraser University, but with a “big asterisk.”
“The recent evolution of bird flu is a real concern,” said Dr. Brinkman, who tracks the evolution of avian flu viruses. She said the D1.1 genotype of H5N1, which severely sickened a patient in Louisiana this week and a British Columbia teenager last month, and the unrelated discovery this year of bird flu in cows in the United States are cause for caution.
California declared a state of emergency on Wednesday over the outbreak of avian flu in dairy cows. The H5N1 virus has not yet been detected in Canadian cattle. Both the B.C. and Louisiana cases are believed to be connected to birds.
The Louisiana resident, who is over 65, was admitted to hospital in critical condition after suspected contact with an infected backyard flock. An investigation into the B.C. adolescent, whose age and gender are not being released by the province, concluded that their case is likely connected to wild birds, not farmed poultry.
The B.C. young person was in critical condition but their current status is unknown. The province declined to give an update on the teenager’s case on Thursday.
There is no evidence of sustained human-to-human transmission of avian flu and health officials across Canada have stressed that the risk to the general public remains low despite widespread infections detected in domestic and wild birds.
“But this is the first winter where we’re going to have seasonal flu mixing with that flu and we’re just not sure what’s going to happen,” said Dr. Brinkman. She said there is potential for a reassortment virus, which is created when two or more viruses mix with one another and create a new infective agent.
Allison McGeer, an infectious-disease physician at Sinai Health System in Toronto, said one of the problems in Canada is that most data on the respiratory viruses capture a moment in time rather than the current situation.
“When the season is starting, that’s a big gap,” Dr. McGeer said. She said it is still too early this season to determine the predominant influenza A strain, though H1N1 is currently the ruling subtype over H3N2.
The difference, she explained, is that people can accumulate protection against H1N1 over a lifetime so the virus tends to affect children more than adults, which can result in increased visits to pediatric emergency departments and family physician offices. Whereas H3N2, because it evolves faster and there is not that same protection, leads to more disease in older adults than in children and can be particularly brutal for places such as nursing homes.
Either scenario doesn’t play well in places such as Manitoba and Ontario where emergency-department closings are expected to take place over the holidays.
Joss Reimer, president of the Canadian Medical Association and a hospitalist in Winnipeg, said a staffing crisis in Manitoba is affecting the health care system overall but it is most obvious in emergency departments.
“Cardiologists have this expression that time is muscle when it comes to heart attacks. And that means, that if we don’t respond quickly, that’s going to cost the heart muscle,” she said. “We don’t want people delaying care because their ER isn’t open until a certain hour, but that might be the reality for some communities.”
With a report from Kelly Grant in Toronto
