Pertussis, commonly known as whooping cough, is continuing to spread through Anaconda and now Butte.
The number of cases in Anaconda has now passed 20. Butte-Silver Bow health officials tell us pertussis has now shown up in a Butte High School student.
Pertussis is a highly contagious bacterial infection of the respiratory system.
"As of noon today we only have one confirmed case in Butte-Silver Bow and that is in a high school student at Butte High,” said Karen Maloughney, a nurse at the Butte-Silver Bow Health Department.
One case doesn't seem like much to most, but when you hear how easily pertussis spreads it can cause some concern, and Butte Health Officials are taking this case seriously.
"We went up to the school and got the seating charts of the student and all of those kids who are considered close contacts, which is anybody who is within in arm's length, within an hour period of time," added Maloughney.
We asked why exactly Pertussis spreads so easily. Maloughney told NBC Montana a lot of it has to do with how long it can take for the symptoms to show up.
"The incubation period is 21 days so you could actually have pertussis and not know it," she said.
While the health department is treating those who may have come into contact with the student, Maloughney says vaccination still offers the best protection.
"The best way to prevent pertussis is to get vaccinated. That is the standard, the best way not to get it," concluded Maloughney.
A majority of people are vaccinated for pertussis at a young age.
There is also an adult version of the vaccine available and health officials highly recommended getting the vaccine before it's too late.