Cases of invasive infection on the rise in part of Ontario


Published June 18, 2024 at 9:20 am

Anthony Urciuoli/ photo

Over the past two years, public health officials have encouraged people to exercise increased vigilance after noting small but significant increases in some dangerous invasive bacterial infections that could, if left untreated, lead to disability or death.

Now, Toronto Public Health is asking people–especially those about to participate in events that involve close contact with sizeable crowds–to ensure they are up to date on vaccinations in the wake of a small but sharp increase in cases of invasive meningococcal disease (IMD). Recently, the TPH said it has recorded 13 cases of the disease since the start of the year, with two people succumbing to the illness. 

It says this is the highest caseload in over 20 years. 

“The average number of cases seen in a year is six, and we have already had 13 into early June, so we can expect to see more cases this year,” Dr. Vinita Dubey, associate medical officer of health with Toronto Public Health, said in an email to 

“Cases have occurred among those who have travelled and those who have not travelled. The last time we had 13 cases in a whole year was in 2002.”

But while many public health units have reported increases in other diseases, such as invasive Group A Streptococcus (iGAS) and measles, not every unit is seeing more IMD. Public Health Ontario says it isn’t seeing unusual IMD activity outside of Toronto but has noticed an uptick over 2020 and 2021–years when contact was limited due to COVID-19 restrictions.

Peel Public Health, which serves Mississauga, Brampton and Caledon, said that several countries, including the United States, are reporting increases in cases of IMD. The disease, caused by the bacteria Neisseria meningitides, is often severe and can be deadly. It can manifest as infections in the lining of the brain and spinal cord (meningitis) and the bloodstream. 

TPH says that people can carry the bacteria in their noses and throats and not get sick. In rare instances, the bacteria can cause meningitis (a brain infection) or septicemia (a blood infection). In some cases, it can lead to serious complications such as hearing loss, brain damage, limb loss, and death.

Symptoms that people should be on the lookout for include fever, aches, joint pain, a headache, a stiff neck (a headache with a stiff neck is considered an alarming symptom that requires prompt medical attention) and increased sensitivity to light. 

People spread meningococcal bacteria to others by sharing respiratory and throat secretions (saliva) and, unlike other respiratory diseases, close and prolonged contact is generally required for the infection to pass from one person to another. 

“Since 2000, there has been an overall decrease in the incidence of reported invasive meningococcal disease (IMD) in Ontario, likely related to the implementation of routine meningococcal vaccine programs for children and youth,” a Public Health Ontario spokesperson told in an email. 

That said, public health officials say it’s never a bad time to check your–or your children’s–vaccination records to ensure you’re as protected against IMD as possible. Health officials say the first vaccination against meningococcal disease is offered to children at one year of age. Pre-teens can also be vaccinated at the age of 12. People born in 1986 or later who have not previously received a meningococcal vaccine can check with their doctor and receive a dose free of charge. 

“Peel is not observing an increase,” a Peel Public Health spokesperson told in an email, adding that the region has recorded one case of IMD since Jan. 1. 

The region also recorded a single case in 2023. 

“We are not seeing an increase in community spread. Keeping up to date with recommended vaccines is the best protection against IMD,” the spokesperson said. 

Peel Public Health says outbreaks can occur during mass gatherings and during travel. For that reason, the health agency recommends that travellers protect themselves with vaccination. 

“IMD cases have occurred previously in conjunction with mass gatherings, including the Hajj pilgrimage and international Pride events,” the spokesperson says. 

“IMD can affect people of any age. However, it is most common in children under five years old, teens, and young adults who are not vaccinated against the disease.”

But while some areas are seeing an uptick, infectious disease experts say the risk of wide community spread is low. 

“When you look at diseases over time, you see random clusters of cases. This doesn’t mean we’ll suddenly see a huge number of them. But in the last six months, we’ve seen more than we expected,” Dr. Sumon Chakrabarti, an infectious disease physician at Trillium Health Partners in Mississauga, told

“I don’t think we’re seeing an epidemic wave.” 

Chakrabarti says current vaccinations are quite good at preventing IMD by covering several strains of meningococcal infection that can make people sick. While vaccines that cover strains A, B, C, Y, and W-135 are available, the recommended shots do not necessarily cover every strain–only the most commonly seen ones. 

“We have pretty good vaccines for [IMD] now,” Chakrabarti says, adding that the meningococcal conjugate (Men-C-C) vaccine offered to children at 12 months of age protects against meningococcal C infection and the meningococcal quadrivalent conjugate (Men-C-ACYW-135) vaccine offered to children at 12 protects against A, C, Y and W-135. A separate vaccination for type B is available but not given routinely. 

“The vaccine works well. We occasionally see cases, but because of vaccination, we don’t see as many outbreaks as we saw 30 years ago,” he says. 

When asked why the B strain isn’t covered in routine vaccination, Chakrabarti says most infections are still related to the C strain. 

“Once you’ve been given a certain vaccine for enough time, people get protected against that one serotype, so you might start to see other serotypes that are not covered. We don’t have routine coverage for all five serotypes,” he says. 

He says there are no indications at this time that B serotypes will be routinely targeted in shots, and he does not know whether that will change. 

“The thing with IMD is the outbreaks tend to be very localized. Measles can easily affect a full population, so a universal program makes sense. Kids can get Men C, but Men B is not as widespread and hasn’t been shown to be a problem, so it’s better to do something more targeted.” 

Chakrabarti and other health experts say the risk of community spread remains low despite the current influx in cases in Toronto, as transmission tends to occur in places where people are living in close proximity. 

“You generally see [IMD] in areas where younger individuals congregate, such as high schools, dormitories and army barracks,” he says. 

“The other big one applicable to people [in the GTA] is the Hajj to Mecca. One of the strong recommendations is getting the vaccine before the Hajj or visiting the meningitis belt.” 

According to the World Health Organization, more significant amounts of IMD are seen in a region of sub-Saharan Africa known as the African Meningitis Belt. Countries where the risk is higher include the Gambia, Senegal, Guinea-Bissau, Guinea, Mali, Burkina Faso, Ghana, Niger, Nigeria, Cameroon, Chad, Central African Republic, Sudan, South Sudan, Uganda, Kenya, Ethiopia and Eritrea.

The WHO says people who live in crowded conditions, such as in refugee camps or overcrowded homes, are more at risk, along with people with HIV or other immunocompromising conditions. The risk is also high for children under five and adolescents. 

As for why Toronto is seeing an outbreak and other parts of Ontario are not, TPH’s Dubey says local outbreaks are not unprecedented and cases have been observed in people who come from countries where routine vaccinations are not as accessible. 

“IMD is relatively rare in Toronto but there have been outbreaks from time to time, including in 2022 when TPH simultaneously reported three cases in people born outside of Canada in countries where routine childhood immunization against the disease was not provided,” she says. 

“Meningococcal disease outbreaks have occurred previously in conjunction with mass gatherings, including the Hajj pilgrimage.”

Chakrabarti also says the density of Toronto and the larger gatherings that tend to take place could prompt the occasional outbreak.

Fortunately, he doesn’t expect cases to grow significantly. 

“We see stochastic spread and there might be certain clusters. Pride, for example, happens downtown rather than in the suburbs. Maybe we will see more cases coming up, but my speculation is that this is a temporary cluster that we’re seeing and not indicative of an increased rate for a sustained period of time.”

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