Walking pneumonia cases may be rising in Canada. Here's what ...

Mycoplasma pneumoniae, also known as walking pneumonia, is generally a mild bacterial infection that largely affects children and teens and can commonly be treated with antibiotics.

The infection got its informal name because people infected with it are generally not as ill as those with other types of pneumonia.

"It's called walking pneumonia because many people aren't sick enough to be flat out on their back at home or in a hospital," said Dr. Isaac Bogoch, an infectious disease specialist at Toronto General Hospital.

"Many people can carry on about their daily routine feeling crummy but not sick enough to be staying at home. Having said that, that's just a colloquial term, and of course we know it can make some people very sick."

In October, the U.S. Centers for Disease Control and Prevention (CDC) reported a rise in cases of Mycoplasma pneumoniae infections, especially in young children. The increase started in the late spring, and case counts have remained high.

Canada does not track the number of cases of walking pneumonia, but anecdotally, doctors say they have seen an increase in cases.

Dr. Earl Rubin, a pediatric infectious disease specialist at the Montreal Children's Hospital, said since the summer, he's seen patients being admitted to the hospital and testing positive.

"Speaking to colleagues across the country in pediatric infectious diseases, everybody is experiencing the same," Rubin said.

"We have received some signals of increased traffic in Quebec and are monitoring the situation," the province's Health Ministry said in a statement.

Halifax hospital IWK Health reported a total of 11 cases last year. So far this year, there have been 113 cases, including 28 pediatric inpatients.

The B.C. Centre for Disease Control said its surveillance indicates that the province is seeing more respiratory infections due to M. pneumoniae than in previous years — most notably among people under 20 — and it is monitoring the situation closely.

B.C. Children's Hospital in Vancouver also recorded an increase in children presenting with walking pneumonia at the emergency department since August.

What causes it?

The respiratory infection is caused by the bacteria Mycoplasma pneumoniae.

It spreads through the air, Bogoch said. This includes when a person coughs or sneezes, the CDC said.

Who gets it?

The infections can occur at any age, but they are most often found in children ages five to 17 and in young adults. The CDC called the increase since March in children aged two to four "notable because M. pneumoniae historically hasn't been recognized as a leading cause of pneumonia in this age group."

Adults can also be affected. If someone has the infection, you can expect a third of the household to get it, Rubin said.

What are the symptoms?

M. pneumoniae infections are generally mild and mostly present as a chest cold, with fever, cough and fatigue.

In about a quarter of cases, pneumonia can occur, meaning the lungs are involved, Rubin said.

Nausea, vomiting or loose stools may also occur.

What's the treatment?

Doctors typically diagnose the infection based on a patient's signs, symptoms and history without waiting for confirmatory lab test results.

The majority of people will get better on their own, doctors say.

Rubin said the bacteria are considered atypical because they're missing the cell wall that some other pneumonia antibiotics act against.

"Azithromycin is a very common, widely available antibiotic that would be used to treat this infection," Bogoch said. "There's other options as well."

Why are cases on the rise?

There are a few lines of thinking on why more cases of M. pneumoniae are being seen now, following the precautions of the COVID-19 pandemic.

"One potential hypothesis is that there are more people who are not immune to it and therefore more susceptible," Rubin said. "You combine that with something that is quite infectious, you can expect the numbers to go up."

There's no evidence the bacteria itself changed, he said.

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Pediatricians say most kids can be treated at home. They need to stay hydrated, be given age-appropriate medicines to bring down fever as needed and rest.

Rubin said the infection has been associated with wheezing that looks like asthma or can exacerbate existing asthma.

"If somebody is having respiratory distress, if somebody is much sicker than they are used to seeing with their regular run-of-the-mill cold, then for sure ... seek medical attention," he advised.

Dr. Carlye Jensen, an emergency and family physician at Oak Valley Health's Uxbridge Hospital north of Toronto, said pneumonia can sometimes follow a viral infection like a cold.

That's why if someone feels better and then suddenly starts to get sick again, especially in the chest, or a fever starts, it's worth getting checked out, she said.

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More difficulty breathing, dehydration or lethargy are all signs that a child should be seen by a physician, doctors generally advise.

Prevention tips reinforced

British Columbia health officials recommend that people stay up to date with immunizations, including updated COVID-19 and influenza vaccinations, as well as routine vaccines for children.

"There are vaccines to protect against certain types of pneumonia caused by Streptococcus bacteria. Although these vaccines will not directly prevent M. pneumoniae, they can reduce the likelihood of secondary bacterial infection due to M. pneumoniae or the likelihood of more severe illness due to viral co-infection," a spokesperson for the B.C. Centre for Disease Control said in an email.

To prevent all respiratory infections, people are advised to clean their hands regularly, stay home when sick, especially if they have a fever, wear a mask in indoor public places if they're able to and can do so safely, and cough and sneeze into their elbows.