BOISE — Health officials say a whooping cough outbreak has now sickened roughly 122 people in southwestern Idaho, and they're warning those numbers could increase with the start of the school year.

Whooping cough, also called pertussis, can be avoided with a series of vaccines. But the illness can be serious or even fatal for infants because the vaccine series takes multiple months to complete.

Cases of pertussis have been found throughout the Southwest District Health region, which includes Adams, Canyon, Gem, Owyhee, Payette and Washington counties. But the bulk of them have occurred in Canyon County, where 94 people have contracted the disease.

District environmental health supervisor Jami Delmore says people who have a cough that lasts two weeks should see a health care provider to determine if the illness is pertussis. The disease is treatable with a five-day course of antibiotics.