Whooping cough still spreading as southern Alberta outbreak grows

Dozens more cases of pertussis, also known as whooping cough, have been identified as an outbreak in southern Alberta shows no signs of letting up.

And sporadic cases of the highly contagious disease, which can be prevented through vaccination, are popping up elsewhere in the province.

In all, 304 Albertans have tested positive for whooping cough this year. That includes 279 cases in the south zone, where an outbreak was declared in January.

According to Alberta Health Services (AHS), 53 new cases have been identified in the province since mid-June. It could not say how many of those cases were found in the south zone.

But previous data provided by AHS pegged the south zone outbreak at 186 cases in May, showing a two-month increase of 93 cases.

"We really do want to try and get these cases back under control, identify the sources, limit the spread and get this out of the community before kids go back to school in the fall," said Craig Jenne, a professor in the department of microbiology, immunology and infectious diseases at the University of Calgary.

The health authority said 75 per cent of the province's cases this year have been in children under the age of 10.

Seven children, including six in the south zone and one in central Alberta, have been hospitalized.

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In the central zone, 17 cases have been identified, while the north zone has had seven, and one case has been found in the Calgary area.

AHS said one of those cases has been linked to the southern Alberta outbreak.

Immunization rates dropping

Pertussis is a bacterial infection that causes severe coughing that can last weeks or months.  According to AHS, it can lead to pneumonia and "in rare cases seizures, brain injury and death."

The best protection, Jenne said, is vaccination.

But Alberta Health data shows immunization rates have dropped dramatically in recent years, with 58 per cent of children in the south zone up-to-date on their pertussis vaccine doses by the age of two in 2022, compared to 76 per cent in 2008.

The provincial average, which has also declined, sat at 71 per cent last year.

"Diseases like pertussis are actually some of the most infectious diseases we've ever identified. And we need greater than 90 per cent of the community to be vaccinated to have any form of herd immunity, to protect and limit the spread of virus," said Jenne.

Immunization coverage varies widely in southernmost health zone, from a low of 22 per cent in the County of Forty Mile to 79 per cent in West Lethbridge.

"So right now, we know that the vaccine rates are far below that, and it really was a matter of time before we started to see pertussis spreading in the community."

Newborns and neonates are at the highest risk for severe illness, according to Jenne.

"As those vaccine numbers go back down, unfortunately we as a society are no better protected than we were before vaccinations. So we're still at risk. This is a disease that every couple of years we do hear, tragically, of the loss of life," he said.

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While there have been hospitalizations, AHS said no deaths have been attributed to this outbreak.

It is urging parents to ensure their children are immunized.

"Cases in the south zone have been reported in most communities between Fort Macleod to Medicine Hat, including Brooks," AHS spokesperson Gwen Wirth said in an emailed statement.

The health authority has been messaging for weeks that southern Alberta is experiencing community spread.

"Cases have been identified at schools and other community locations such as churches and sites where children gather to take lessons," said Wirth.

"Public Health is unable to identify linkages between most of the recent cases, indicating there is likely more disease circulating in communities that is not being reported."

According to AHS, 461 cases were reported during the last large pertussis outbreak in the south zone in 2017.