This Gram-stained photomicrograph depicts Bordetella pertussis bacteria, which is the etiologic pathogen for pertussis, also known as whooping cough. Credit: Courtesy of Centers for Disease

Already the state with the highest rate of whooping cough in the country, Maine is on track to see even more cases this year than last.

The bacterial infection also known as pertussis results in a violent, hacking cough. Maine’s rate of the disease is eight times the national average, and there were nearly 450 cases last year.

There were 95 cases of the disease through February. That’s more than double the count from 2018, when there were 40 through February, the Portland Press Herald reported. The Maine Center for Disease Control & Prevention is looking into the uptick.

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More vaccinated people are getting the disease because the bacterium that causes it has mutated, said University of New England biomedical sciences professor Meghan May, who researches pertussis. She is the author of a research paper about the mutation of the bacterium that is expected to be published in a journal this spring.

May said the research could “provide a road map” to a more effective vaccine. In the meantime, the existing vaccine is safe and reasonably effective, although Maine schools have higher opt-out rates than many states. The Maine Legislature is considering a law change that would remove philosophical and religious exemptions from school vaccinations.

Maine’s high opt-out rate has led to outbreaks in some schools.

One such outbreak has resulted in 11 confirmed cases at Falmouth High School. The district has canceled a chorus concert planned for Thursday night as a result.

“Given we do not yet have any confirmed cases of pertussis at the middle or elementary schools, I feel it is prudent to reschedule this event and continue taking appropriate measures to keep our students and community members as healthy as possible,” Falmouth Public Schools operations supervisor Jessica Duplisea said in an email to the school community.