The Kennebunk-area school district issued a health alert Friday following a confirmed case of pertussis at Sea Road School.

Regional School Unit 21 was notified of the case by the Maine Center for Disease Control and Prevention, according to a letter to parents and guardians from Superintendent Terri Cooper. The district has six schools and includes the communities of Kennebunk, Kennebunkport and Arundel.

Pertussis, or whooping cough, is a bacterial infection that causes a violent, persistent cough. The illness is spread person to person through coughing and sneezing and usually begins with symptoms of a common cold such as sore throat and runny nose, often leading to a severe cough that can last for weeks.

Most children are vaccinated against pertussis, but it is still possible for vaccinated children to become ill, the superintendent said in her letter. Babies are most at risk of serious illness.

Cooper asked that parents and guardians keep home children if they have a severe cough or a prolonged cough lasting two weeks or more, and that they contact their healthcare providers. She also recommended that parents check with their healthcare providers to make sure they and their children are up to date on pertussis vaccinations.

In 2019, prior to the COVID-19 pandemic, Maine had one of the highest rates of pertussis in the country at 28.49 cases per 100,000 people. However, cases have sharply declined over the last few years, something the Maine CDC has attributed to COVID-19 restrictions as well as a new school vaccine mandate that went into effect in the 2021-22 school year.

As of Nov. 25, there had been 92 pertussis cases reported in Maine in 2022. That compares to 383 cases for all of 2019, and 446 cases in 2018, when Maine’s pertussis rate was the worst in the nation.