Southern Alberta is seeing a surge of cases of pertussis, or whooping cough, and a health official says it's directly related to low immunization rates in some areas.

As of Thursday morning, 38 cases in the Lethbridge area have been linked.

"We are getting multiple lab reports a day and we are definitely seeing this outbreak taking off at an exponential rate," Vivien Suttorp, Alberta Health Services' lead medical officer of health for the south zone, told CBC News.

"We have had a lot of individuals and children exposed to cases of whooping cough and we have a lot of individuals who are not immunized at all."

Suttorp warns those are just the confirmed cases and that whooping cough can often go unreported.

vivien suttorp AHS

'In southern Alberta there is a big difference between communities and between schools in immunization uptake,' health official Vivien Suttorp warns. (Sarah Lawrynuik/CBC)

"Individuals who have an ongoing cough for two or three months may not know that they have whooping cough because symptoms can be mild in adults and older children. It's the very young ones that are mostly likely to come to a physician's attention," Suttorp explained.

"There are many, many more out there that we are not aware of."

Immunization rates in southern Alberta can vary significantly.

The Fort Macleod area, for example, ranks nearly dead last out of 132 local health zones in Alberta, but the neighbouring community of Pincher Creek — immediately to the west — ranks among the highest.

The name of one particular church — the Netherlands Reformed Congregation — often comes up when talking about vaccination rates in the Fort Macleod area.

Suttorp says school outbreaks really illustrate that difference.

"The good news is that most schools have very high immunization and typically we will see only one or two cases in those schools. Some schools where we have maybe 10 per cent or 20 per cent of children immunized, we will see ongoing cases over many, many months," she said.

"In southern Alberta there is a big difference between communities and between schools in immunization uptake."

All of the cases of whooping cough in southern Alberta have been locally acquired, Suttorp added.

With files from Robson Fletcher