New data from Public Health Ontario shows the number of confirmed cases of pertussis, known commonly as whooping cough, began rising across the province in May – and several area health units say the situation has only gotten worse since then.
At least six health units have issued public notices since June and two others have confirmed to Global News that they have observed a higher-than-normal number of cases. While the initial stage of the respiratory infection can often be mistaken for the common cold, it can cause severe illness and even death in vulnerable populations and is extremely contagious.
Public Health Ontario’s latest data, updated July 17, only covers up to the end of May, but it shows that while cases were below a pre-pandemic five-year average (from 2015-19) in February, March and April, cases were above the pre-pandemic average in May — and the increases were not confined to any specific region.
Pre-pandemic data is used because case counts dropped significantly during the height of the COVID-19 pandemic amid lockdowns, mask mandates and social distancing. For example, between January and May of 2021 there were only two cases confirmed in Ontario while the same timeframe in 2022 saw nine cases.
The total number of confirmed cases between January and May was 127 in 2019, 147 in 2018 and 151 in 2017. Between January and May of this year, that number is 206.
A summer surge
PHO says the jump in cases in May was “not above a threshold considered to be significantly elevated,” but figures for June and July are not yet available and several health units are reporting concerning jumps in the last two months.
Toronto Public Health told Global News that cases so far this year are significantly higher than average.
“As of July 23, 2024, there have been 68 pertussis cases in Toronto, double the 5-year pre-pandemic average of 29 cases for the same period,” Dr. Allison Chris, associate medical officer of health for Toronto Public Health said.
“As we continue to investigate these cases, we’re reminding residents about the importance of vaccination. Pertussis is a highly contagious and vaccine-preventable infection that can cause severe illness in infants, young children and pregnant individuals. The best way to prevent pertussis is to make sure you and your children are vaccinated.”
The Middlesex-London Health Unit said it is seeing more cases than usual, “like several of our health unit colleagues across the province.” There have been seven cases reported to the MLHU since May, a spokesperson said Tuesday.
“These cases were not linked to one another, so no outbreak has been declared,” the spokesperson said.
“We suspect that the increase in cases is related to slighter lower vaccination rates post-pandemic. However, we’re pleased to share that our Vaccine Preventable Diseases team has been working diligently to catch children up on their routine childhood immunizations and our vaccination rates are now reaching pre-pandemic levels.”
Earlier this month, Southwestern Public Health — which covers Oxford and Elgin Counties and the City of St. Thomas – reported that there had been 31 cases of pertussis confirmed in the region since the beginning of May.
Last week, the Brant County Health Unit reported 12 confirmed cases in the last two months, which is “significantly higher than what is typical for our community.”
“There has not been a confirmed case of pertussis in Brantford-Brant since 2020.”
Ottawa Public Health said there were 10 total cases of “confirmed or probable pertussis” between Jan. 1 and July 8, up from six cases for all over 2023.
Leeds, Grenville & Lanark District Health Unit did not provide figures but said it was “raising awareness” of the “potential for spread” in the region, while the Eastern Ontario Health Unit warned of a “concerning increase in cases,” without providing a figure. The Haliburton, Kawartha Pine Ridge District Health Unit issued its own alert in early June.
Cases may be underreported
Pertussis is a respiratory infection caused by the bacterium Bordetella pertussis and is spread person-to-person through contact with respiratory droplets from an infected person coughing or sneezing.
Public Health Agency of Canada says studies show pertussis has “80 per cent secondary attack rates among susceptible household contacts,” meaning if someone in a home is infected, there’s an 80-per cent chance of the illness spreading to another susceptible individual in that same household.
According to a Public Health Ontario report from 2022, the disease tends to be “under-diagnosed” because of the “non-specific nature of the clinical presentation of pertussis.” As a result, PHO says it should be considered as a possibility in anyone presenting with “clinically compatible signs and symptoms.”
Major symptoms include coughing fits that seem to come out of nowhere; a cough ending in “vomiting or gagging, or associated with apnea;” a cough with the “whoop” sound that gave the illness its name; or any cough illness lasting at least two weeks.
The distinctive “whoop” sound can be heard on the PHAC’s website.
Public Health Ontario notes that the “whoop” sound may not always show up in infants and in people who have been vaccinated against the illness. While infection may still occur in people who’ve been vaccinated, PHO says they are less likely to experience severe illness and less likely to spread the illness to others who are also vaccinated.
Infected infants “may require hospitalization due to respiratory distress, pneumonia, apnea, seizures, encephalopathy, hypotension and shock.” The agency says in many cases, it’s later discovered that a close contact of an infant with pertussis had a “history of prolonged cough and no fever.”
Those looking to inquire about their vaccination record or with general vaccination inquiries can find contact information for their local health unit through the Ontario Ministry of Health’s public health unit locator tool.