SKOWHEGAN, Maine — Maine public health officials say they have confirmed three cases of whooping cough in Skowhegan schools.

Superintendent Brent Colbry says a letter was sent home with students Thursday alerting parents and families about the contagious disease, especially those who have been in close contact with the sick students.

Whooping cough, also known as or pertussis, is a contagious respiratory disease that can cause long, violent coughing fits and the characteristic “whooping” sound.

The state epidemiologist told the Morning Sentinel two cases were reported among older students and a third case involved a 7-year-old child. Dr. Stephen Sears says there has been in increase in cases in Maine in the past nine months.

School will be in session Friday, but officials are urging people showing symptoms to seek medical attention.