Ontario has seen a surge in walking pneumonia cases this year, primarily among children, with a positivity rate more than three times higher than pre-COVID levels, according to new figures.
Public Health Ontario said in a report that 733 of 4,069 polymerase chain reaction or PCR tests came back positive between Jan 1 and Nov. 15, amounting to 18 per cent. It wasn’t until May, however, that positive cases began showing up in higher percentages. Positivity rates reached between 25 and 30 per cent monthly between August and November.
Public health agencies across Canada do not typically track walking pneumonia, or mycoplasma pneumoniae, but health care providers in provinces including Quebec, Ontario and British Columbia said they have seen an unusual spike in the bacterial infection in recent months. The U.S.’s Centers for Disease Control and Prevention in October also reported an increase in cases, particularly among children, in that country around spring, which have since remained high.
Most cases of walking pneumonia are mild with symptoms that include a sore throat, coughing, headache, fatigue and fever. But it can develop into a more serious lung infection, known as pneumonia, if left untreated.
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Julianne Kus, a clinical microbiologist with the Public Health Ontario laboratory, said it came as no surprise that rates increased when compared with peak COVID years – 1.3 per cent in 2020 and less than 1 per cent in 2021, 2022 and 2023 – because of public-health restrictions. But this year’s figure is also well above the prepandemic positivity rate of 5.8 per cent in 2019.
Dr. Kus said it is possible that the increase is part of the natural cycle of walking pneumonia that re-emerges every three to seven years, “but it’s the highest numbers we’ve seen in many, many years.” She said collecting data on walking pneumonia raises awareness of its prevalence, which helps physicians and public-health units understand what is happening in their communities so they can address the issue head-on.
Children aged five to 17 had the highest number of positive tests, averaging about 45 per cent, followed by those between ages one and four at 25.5 per cent, according to the Public Health Ontario report published Friday. The positivity rate for people 18 and above was 4.6 per cent.
Public Health Ontario also tested for markers of antimicrobial resistance after reports that some patients were not responding to typical antibiotics, Dr. Kus said. Molecular testing found that 16.3 per cent of the positive PCR tests harboured mutations. She said this was an important finding because it clearly suggests to care providers that it is “reasonable to switch to another class of drugs” to treat walking pneumonia.
Earl Rubin, director of the infectious disease division at the Montreal Children’s Hospital, said he has also seen a “tremendous increase” in recent months, and that he has “never seen it to this degree.” But, because there is no obligation to surveil or test for walking pneumonia, there is no specific data on how pervasive it is. He noted that PCR testing is Quebec is difficult to come by.
He said soaring infections are likely linked to two factors: lowered population immunity since the COVID-19 pandemic and the bacterial disease being highly-contagious with a household attack rate between 25 and 30 per cent.
People can get walking pneumonia by breathing in air droplets of an infected person who coughs or sneezes. The CDC states that most people who spend a short time with someone infected with walking pneumonia don’t get sick but the longer the exposure, the higher the chances are of getting sick.
The B.C. Children’s Hospital and the B.C. Centre for Disease Control said in a joint statement that they have also recorded an increase in children presenting to the emergency department with walking pneumonia since August. They noted that cases are not reported to public health but that laboratory data has shown that cases are higher than in previous years, particularly among people younger than 20.
Alberta Health said in a statement that the ministry has no data that tracks the number of cases because walking pneumonia is not a notifiable disease in the province.
Similarly, James Winkel, a spokesperson with the Saskatchewan Health Authority, said in a statement that the province does not track walking pneumonia cases. He added, however, that the province’s emergency departments, including the Jim Pattison Children’s Hospital, “have not reported the prevalence of this illness at this time.”