MASON CITY, Iowa (AP) — Health officials in northern Iowa have confirmed seven cases of whooping cough in Cerro Gordo County. Mason City television station KIMT reports that the Cerro Gordo County Department of Public Health says it’s investigating instances of the highly contagious disease in the Mason City Community School District and among staff at a local McDonald’s restaurant.

Whooping cough, or pertussis, is spread when infected people cough or sneeze. It starts like the common cold but can progress into violent coughing spells.