Experts are watching closely as cases of invasive pneumococcal disease rise in Alberta.
The potentially life-threatening illness is caused by bacteria known as Streptococcus pneumoniae, which often strike after viral illnesses.
These bacteria — including 100 different variations — can live in the respiratory tract, in many cases triggering no symptoms at all. In their milder form they can cause problems such as middle-ear infections.
But when they invade normally germ-free parts of the body, and become invasive, people can develop pneumonia, meningitis and sepsis.
"At all age groups there's been an increase in the cases and an increase in the rate of cases to the highest levels that I've ever seen," said Dr. Jim Kellner, a University of Calgary infectious diseases specialist who's been studying invasive pneumococcal disease patterns in Calgary since 1998.
"It's a concern to see the kind of numbers that that we've seen. We expected to see big numbers last year. The sustained big numbers this year are a concern."
Provincial data shows cases of invasive pneumococcal disease jumped to 812 last year from 481 in 2018, with a drop in 2020 and 2021 which doctors attribute to pandemic-related restrictions.
The trend comes at the same time as rates of invasive group A strep also rise in Canada.
Hospitalizations for invasive pneumococcal disease jumped to 681 from 398 over the same five-year period and the number of deaths increased to 62 from 42.
Hospitalization and death rates per population are on the rise too, according to numbers provided by Alberta Health.
While the vast majority of severe cases reported last year were in adults, 44 of the 681 people hospitalized in 2023 were under the age of 18 and two children died.
Dr. Jim Kellner is an infectious disease specialist at Alberta Children's Hospital. He's been studying invasive pneumococcal disease patterns in Calgary since 1998. (Submitted by COVID-19 Immunity Task Force)
"It's worrisome anytime we see increases in numbers of infectious diseases," said Dr. Sam Wong, a pediatrician at Edmonton's Stollery Children's Hospital and president of the section of pediatrics with the Alberta Medical Association.
Wong has treated several children over the last few weeks who've ended up in the ICU after developing pneumonia with large collections of fluid around their lungs requiring a chest tube.
"Draining over a litre of fluid from a five year old kid — that's a large volume. Then they decompensate and they end up having to be intubated and require ventiliation support as well as blood pressure support."
According to Kellner, mortaility rates for invasive pneumococcal disease in the Calgary zone are as follows:
children (under 18): 3 per cent
adults over 18: 10 per cent
seniors 65+: 15 per cent
over 85: 25 per cent
"Despite it being a perfectly treatable disease with antibiotics, in the most severe cases, in these invasive cases, you still have a notable mortality rate," he said.
Connection to viral surges
The reasons behind the invasive pneumococcal disease surge are complex, according to Kellner.
Because pneumococcal disease often manifests as a secondary infection, he has no doubt recent viral surges play a key role.
Dr. Sam Wong is president of the section of pediatrics with the Alberta Medical Association. He works at the Stollery Children's Hospital in Edmonton. (Submitted by Sam Wong)
Viral infections spark inflammation in respiratory passages, he said, making it easier for bacteria to invade.
Secondary infections are often limited to the ears and sinuses. But the bacteria can also find their way into the bloodstream and travel to organs such as the lungs and brain.
"With these giant jumps last year with RSV and influenza, and this current year being another huge and early year for influenza, then you expect to see a rise in secondary bacterial infections," he said.
"That's had a huge influence on the rise and the very large number of infections."
Kellner said secondary pneumococcal infections can come after COVID-19 as well, but that appears to happen less frequently.
"It's a numbers game. ... When you have larger numbers of infections, those rare complications become much more common," added Wong.
"It's been quite bad this year with the high numbers of influenza that we've seen."
Provincial data shows immunization rates among children are dropping. In 2008, 90.5 percent of Alberta children were fully immunized with three doses of the pneumococcal vaccine by the age of two. By 2022 that had dropped to 80.8 per cent.
According to Kellner, the vaccines are evolving and new formulations have recently been approved for use in Canada.
"The rise that we're seeing now is related to factors of increases in viral infections and coming out of the pandemic that may settle down over time," said Kellner, who, over the last few decades, has received funding from a number of public granting agencies and pharmaceutical companies for research projects and vaccine clinical trials.
"One can hope that the new vaccines will have an impact to help provide further better control. But we're a long ways away from ... truly controlling pneumococcal disease in the community, locally and globally."