KALISPELL, Mont. -

Flathead County health officials have confirmed that a case of whooping cough has been found in a student at Kalispell Middle School. The most recent case brings the total of Flathead County cases to nine.

Health officials previously confirmed three student cases at the Swan River School in the Bigfork area, and three student cases at Columbia Falls Elementary School. Two adults, one linked to each school, have also come down with the disease.

Health officials say some of the sick had been immunized.

?That could be for a lot of reasons,? said Health Officer Joe Russell. ?It could be that the vaccine wanes a little faster than you think it would. It could be that they?re a little more highly susceptible because of a preexisting condition.?

Russell says that school staff is working hard to minimize the outbreak. Pertussis isn?t just hitting Montana towns. In Washington State, public health officials declared an epidemic and are predicting 3,000 cases by year?s end.