Beyond the numbers: Why the brunt of this year’s flu season came early

Dr. Eddy Lang stood in the hallway of the emergency department of Calgary’s Rockyview General Hospital one evening in early January, wondering how many more patients the hospital could admit.

Ward beds were full and patients awaiting admission had begun to spill out into the emergency department.

“I often describe this as how hospitals across the world use the emergency department as a safety valve. When they can’t get more people upstairs, they just allow people to accumulate in the emergency department,” said Lang, the head of emergency medicine for the Calgary zone of Alberta Health Services.

Registered nurse at Ottawa General Hospital holding needle with flu vaccine prior to administering. Photo by Mateo Peralta.

A total of 15,572 laboratory-confirmed cases of the flu had been recorded across Canada by the end of the first week of January, compared to 8,956 the year before at the same time, a 74 per cent increase.

The majority of cases this flu season are attributed to the H3N2 subtype of Influenza A. But this season, it’s the unexpected early arrival of Influenza B that is crowding hospitals in various Canadian cities.

“Influenza B detections to date are higher than has been observed over the past seven seasons,” reads the Public Health Agency of Canada’s (PHAC) FluWatch report.

The flu hits ahead of schedule

Last season, Alberta saw 3,793 lab-confirmed cases of Influenza A and 701 cases of Influenza B. Calgary represented the highest percentage of cases among Albertan cities at 39 per cent. Out of all cases in Calgary, 86 per cent were Influenza A and 14 per cent were influenza B.

As of Jan. 18, Calgary has already surpassed its total number of lab-confirmed cases from the previous year, 34 per cent of which have been for influenza B.

Dr. Eddy Lang, head of emergency medicine for the Calgary zone of Alberta Health Services. Photo courtesy of Dr. Eddy Lang.

Influenza B typically doesn’t arrive until March, but the unexpected prevalence of Influenza B combined with its emergence over the holidays—a time when doctors’ offices are on reduced hours—led to the spike in flu-related hospitalizations between December and January.

“The flu hit right around Christmas. What are you doing at Christmas? You’re coughing around your uncle at a house party,” Lang said. “Because of that, the infectiousness was more severe than we had seen previously.” 

Flu season outlook and coverage varies between provinces

A similar prominence of Influenza B has been seen across Canada. But while Calgary’s flu season peaked early, Quebec continues to see a steady influx of patients.

As of Jan. 23, seven out of eight hospitals in the Monterégie region of southwest Quebec reported having a stretcher occupancy rate at or exceeding capacity. The measure records the number of patients on a stretcher awaiting admission for up to 24 hours. In Montreal, 14 out of 20 hospitals showed a rate beyond capacity.

“It’s a mixed season because the circulation of A and B are together. That kind of event normally doesn’t happen. Usually the activity of A goes down, then B rises. It’s like you have one or the other, but not both,” said Dr. Renée Paré, a public health officer for Montreal and Quebec.

Entrance to the emergency room at the Ottawa General Hospital. Photo by Mateo Peralta.

Montreal, a city where adults ages 65 years or older are the second largest demographic, according to Canada’s 2016 census, are especially at risk, Paré said.

Seniors are the most susceptible to the flu. Between Aug. 27, 2017 and Jan. 13, 2018, 2,168 people over 65 years old accounted for 68 per cent of all hospitalizations and the majority of FluWatch’s 82 recorded deaths.

Maddison Reid, a senior communications officer with PHAC, said that there are currently contracts with five manufacturers that supply seven different influenza vaccines.

“Since each province and territory decides which vaccines to purchase for its residents, not all of the seven vaccines may be available in each province or territory,” said Reid, who also attributed environmental and demographic factors like climate and population density as potential factors influencing how an urban centre may be affected by the flu.

Public funding for flu vaccines differs between provinces. In Quebec, getting the flu shot isn’t publicly funded for people between the ages of 18 and 59.

As a result, the extent to which a particular region is affected by the flu can vary.

“The Influenza B that is circulating is not in the vaccine, so if people did not get a vaccine last year and even if they get one this year, the strain of B that is circulating is not in the vaccine,” said Paré of Quebec’s vaccine.

“It’s like a prediction. They thought with all the data that the other strain would circulate more, but it’s not what’s happening. I hope the season will be shorter since it’s all together.”

Warnings from Down Under

The severity of this year’s flu season didn’t come as a surprise to Canada’s hospitals, said Dr. Michelle Murti, a physician with Ontario Public Health. Early indications of this year’s flu season were shown in reports out of Australia, where people experienced an overlap in Influenza A and B during its winter in July.

The efficacy rate for the northern hemisphere’s mid-year vaccine isn’t typically available until mid-February, but Murti said that efficacy rates for the vaccine typically range between 40 to 60 per cent.

“There are a few things that are making us concerned about what the actual efficacy of the vaccine will be. We know it’s the same H3N2 strain this year as we had from last year and that was just 42 per cent, so probably less likely to be much better than that,” said Murti, who hopes that a low efficacy rate doesn’t discourage people from getting vaccinated.

Ontario was the only province or territory between 2003 and the 2013-14 flu season that saw a decline in vaccination rates for patients ages 12 and up, according to Statistics Canada.

For that same period, vaccination rates among seniors declined in every province except for New Brunswick and Newfoundland and Labrador.

“We sometimes see confidence go down if people hear that the vaccine didn’t match and wonder what’s the point in getting it, but you do need to get it every year until we have a universal vaccine,” Murti said.

“What you got last year isn’t necessarily going to protect you this year, but there is a benefit in having a vaccine year over year.”

Murti referred to the difficulty of predicting the nature of a given flu season as similar to attempting to hit a moving target. But even if the vaccine isn’t specifically tailored to prevent that season’s strain, research shows that getting vaccinated annually is crucial, especially for seniors.

A Spanish study published by the Canadian Medical Association Journal in January found that adults ages 65 and up who had received four consecutive years of flu shots were half as likely to contract a severe case of the flu.