KALISPELL, Mont. -

The number of whooping cough cases in the Flathead continues to rise. The county health department says five more cases are confirmed, bringing the total to 13.

Four of the recent cases come from middle school students, with one being a contact family member of an an already confirmed case. In an effort to stop the spreading infection, the health department and Kalispell Middle School canceled a concert last night.

Officials tell us 26 tests are pending lab results, and most of the results will come through next week.

"Because we were so early in the progression of our knowledge of the disease there's just too much uncertainty," said Health Officer Joe Russell, "A couple days from now when we have kids that are symptomatic that are being treated, or those close contacts that are being prophylaxed then we'll have a better idea of what we need to do."