It's been a busy day for state lab workers testing for pertussis. The lab had 78 samples to test Monday.
In Missoula County, pertussis cases are holding at seven.
In Ravalli County, one more case leaves the Bitterroot Valley with 48 cases total. Ravalli County public health director Judy Griffin said out of 11 cases the state tested from Ravalli County Monday, only the one was positive.
Ravalli County has the highest number of whooping cough cases in the state.
Pertussis is a highly contagious respiratory illness. Infected people transmit the disease when they cough or sneeze, and someone in proximity breathes in the pertussis bacteria.