There are six confirmed cases of pertussis (whooping cough) in third- through 11th-graders in Bigfork School District, according to Jody White, Flathead Community Health Services director.

Cases started Oct. 29, with the latest one reported Wednesday. Test results are pending in two more possible cases in the school district, White said.

The pertussis outbreak caused the cancellation of today’s Veterans Day assembly that had been planned at Bigfork High School.

Since Oct. 15, there have been 24 pertussis cases in Flathead County. Three of these are in children under 5, but White said these children were not attending any child-care facilities.

“That’s a higher-risk group we’re trying to protect,” White said.

Other schools in which students tested positive recently include Peterson Elementary and Glacier High School in Kalispell, plus Marion and Fair-Mont-Egan.

Bigfork School District Superintendent Cynthia Clary said the district is working with the health department to identify people exposed to pertussis through contact. People exposed to pertussis are recommended to begin an antibiotic treatment to stop further transmission.

“We’d like to emphasize that if someone was identified as a contact, and they test negative, they still need to take the prophylaxis because they could be coming down with it,” White said. “We’ve had two situations in the past week where they tested negative and didn’t take prophylaxis, and a week later they developed pertussis.”

Students who have not been immunized are instructed they need to complete a five-day course of antibiotics or be excluded from school for 21 days — the incubation period for the disease.

Because older adults with compromised immune systems are at high risk of contracting pertussis, the Veterans Day event was canceled as a precaution, Clary said.

White advised people to be vigilant about possible symptoms. The Centers for Disease Control and Prevention said the disease might start with a mild cough or fever that turns into a violent, rapid, uncontrollable cough within one to two weeks. In infants, the cough may be minimal or absent.

She said adults might request medical providers perform pertussis tests if they suspect symptoms are present in themselves or their children.

“Pertussis is often misdiagnosed as bronchitis,” White said.

Reporter Hilary Matheson may be reached at 758-4431 or by email at hmatheson@dailyinterlake.com.