Flu activity slowly decreasing, Public Health Agency of Canada reports

Flu activity is slowly decreasing in Canada and seems to be winding down in the U.S., health officials say.

Kids can experience 'more severe illness that lasts longer,' retired pediatric infectious disease expert says

Young children are particularly vulnerable to the effects of flu infection. (Ryan Remiorz/Canadian Press)

Flu activity is slowly decreasing in Canada and seems to be winding down in the U.S., health officials say.

Friday's FluWatch report from the Public Health Agency of Canada covers the week ending Feb. 28.

"Overall, influenza activity in Canada remains at peak levels," the report's authors wrote. "Influenza activity is slowly decreasing in many parts of the country."

For months, the number of pediatric hospitalizations among those aged 16 and younger has been above the seven-season average, the agency said.

Several flu viruses are circulating, including a type called influenza B that tends to hit children hard. 

For instance, 126 children and teens have been admitted to intensive care units and eight pediatric deaths have been reported. 

The Immunization Monitoring Program Active or (IMPACT) network, which is made up of experts from pediatric hospitals, provides data on pediatric flu cases for the report. 

"It's mainly a pediatric disease," Dr. David Scheifele, a retired pediatric infectious disease specialist in Vancouver who founded IMPACT, said of the flu. "We focus more on its effects on the elderly, the immunocompromised. In terms of sheer numbers, kids bear the great burden of influenza disease."

Scheifele said young children are vulnerable to the effects of flu because they're born without immunity to the four main strains — two influenza A strains and two influenza B strains.

"The first time that you were infected with an unfamiliar influenza strain it causes more severe illness that lasts longer," Scheifele said, adding that children generally shed more viruses, which means they can more readily infect others.

Hospitals struggling

In British Columbia, Scheifele said flu rates are declining but still high.

Flu is also contributing to the strain on children's hospitals in Ontario. CHEO in Ottawa has had to transfer the most critically ill children to hospitals in Montreal, Toronto and Kingston, Ont., and flu is adding to demands in in the emergency department, a official with the children's hospital said. 

Toronto's SickKids anticipates an increase in activity each flu season when there's growing demand for care, a spokesperson said. This flu season was no different — the Toronto hospital said between Dec. 1, 2017, and Feb. 20, 2018, it has had an average occupancy rate of 108 per cent, rising to 111 per cent in February.

Not over — but trending lower 

This flu season has been further complicated by the number of influenza strains circulating at the same, infectious disease specialists say.

"With flu it's kind of like a steeplechase where we have a fairly quick ramp up of activity, a few weeks of intense activity and then it comes back down," said Dr. Michelle Murti, a public health physician at Public Health Ontario. "What we're seeing here is a little bit more of an up and staying up."

In the U.S., the season seemed to peak in early February, the U.S. Centers for Disease Control and Prevention said Friday.

The number of people going to the doctor with symptoms of the flu has continued to decline. Deaths from the flu or pneumonia are going down, too.

"The season's not over but we're definitely on the downward trend right now," said Dr. Anne Schuchat, the CDC's acting director.

Health officials in the U.S. say 114 children have died from the flu so far this season.

With files from the Associated Press