Pertussis cases in Maine ballooned in October, and with 64 cases reported statewide it was the worst month so far this year for the infectious disease, which produces a violent cough.

The October figures bring the total number of pertussis cases to 332 for the first 10 months of 2018, according to the Maine Center for Disease Control and Prevention. Maine consistently has among the highest rates of pertussis – also known as whooping cough – in the nation.

The state is on pace to nearly match the 410 pertussis cases in 2017, which was the most since 557 cases were recorded in 2014. Maine’s pertussis rate of 27.7 cases per 100,000 population was the worst in the nation in 2017 and more than five times the national average, according to the U.S. Centers for Disease Control and Prevention.

Scarborough, Biddeford and Kennebunk schools reported pertussis outbreaks this fall, and on Nov. 8 the Middle School of the Kennebunks canceled its annual community Thanksgiving dinner to avoid potentially exposing the community, especially babies and senior citizens, to the disease. An outbreak is defined as three or more cases in one location, such as a school, day care facility, church or workplace.

York County has been a hot spot for pertussis, with 37 of the 64 cases in October recorded in Maine’s southernmost county, including an outbreak at Ninny’s House Childcare in Buxton.

Health experts cite three major reasons why Maine is vulnerable to pertussis infections: parents opting their children out of school-required vaccines; the waning effectiveness of the vaccine, which requires a booster shot; and Maine being late to adopt a required booster shot for middle school students. The state didn’t establish the requirement until the 2017-18 school year.

Dr. Laura Blaisdell, a Yarmouth pediatrician and vaccine researcher, said the high rates of pertussis are “most likely related to low vaccination rates. We can and should do better.”

Pertussis causes a violent cough, especially in infants and toddlers, that can cause vomiting and exhaustion, according to the federal CDC. The coughing can linger for up to 10 weeks. Pertussis, a bacterial infection, can be treated with antibiotics, but unless caught early, the coughing symptoms can persist even after antibiotics are taken.

Vaccines are overwhelmingly safe and research has proved that they do not cause autism, but myths that the vaccines are contributing to autism have persisted since the late 1990s.

Maine typically has one of the highest rates of parents opting out of school-required vaccines for children entering kindergarten. Opt-out rates increased for the 2017-18 school year to 5 percent of kindergartners for non-medical reasons, on philosophic or religious grounds. Democratic lawmakers have said they intend to introduce bills that would make it more difficult for parents to forgo vaccines for schoolchildren, after Gov.-elect Janet Mills assumes office in January.

Mills has said she’s open to bills that would improve “Maine’s disturbingly low rates of vaccination in some parts of the state.” Outgoing Gov. Paul LePage vetoed an attempt to make it more difficult to opt out, and a Legislature override effort fell five votes short.