BELFAST, Maine — Whooping cough has been on the rise during the last few months in several Maine counties, according to the Maine Center for Disease Control and Prevention.

Since September, the highly contagious respiratory infection has hit Piscatquis County the hardest, at a rate of 122 cases per 100,000 residents, 10 times the statewide average. Two other counties also reported high rates of the disease this autumn, including Waldo County, at 64 cases per 100,000 residents and Somerset County, with 60 cases per 100,000 residents.

Dr. Sheila Pinette, director of the Maine CDC, said Thursday that pertussis generally begins with symptoms of a common cold, then often develops into a severe cough after a few weeks. The cough can last for several weeks, and the disease is most dangerous to infants because it can rob them of oxygen, leading to brain damage and even death.

“Any time you have a child under a year of age, they don’t cough as well,” she said. “Oftentimes, small children under the age of 6 months require hospitalization.”

She said that as of Dec. 10, Maine had a total of 453 cases since the beginning of the year. While that is significantly more than the 332 recorded in 2013, it does not approach the spike of 737 cases amid a national outbreak in 2012 — the highest in at least 50 years.

“Once school started, we started seeing larger numbers across the board,” Pinette said.

Other counties have had much lower pertussis infection rates since September, with very few or zero confirmed cases in Franklin, Hancock, Kennebec, Knox, Lincoln, Oxford, Washington, Cumberland and York counties. Slightly higher rates were recorded in Penobscot County, where 18 cases per 100,000 were recorded; Androscoggin, 17; Sagadahoc, 14; and Aroostook, 11.

In June and July of this year, an outbreak sickened a number of children in Washington County and several other counties in northern and eastern Maine. The numbers dropped before they started to rise again in October and November, according to figures from the CDC.

“We need to immunize and practice good hand-washing and respiratory etiquette,” Pinette told the BDN in August.

Parents should call their physicians if they are unsure whether their children are fully vaccinated, she said Thursday.

Maine is among the top 10 states with the highest vaccine opt-out rates , according to figures from the U.S. Centers for Disease Control and Prevention. More than 4 percent of Maine kindergartners, or 620 students, were exempted from required vaccines in 2012-13, including the vaccine for pertussis. In the majority of cases, parents cited philosophical objections to vaccines instead of medical or religious reasons.

Some parents are hesitant to see their infants and young children stuck with needles numerous times and argue not enough research has been done on the cumulative health effects from so many shots. While some choose to spread their children’s immunizations out over a longer period, medical professionals say vaccines are purposefully timed to be administered when children are most at risk for certain diseases.

Also, though most children in Maine have had the pertussis vaccine before they are 7 years old, immunity can gradually wane over time. A Tdap booster shot — tetanus, diphtheria and pertussis — is recommended for children ages 11 to 18, according to the Maine CDC.

Pinette said if children have a cough that persists for longer than two weeks, parents should call the doctor. The telltale “whoop” is present most, though not all, of the time, she said.

“They’re just constantly coughing,” Pinette said. “You can tell they’re having a hard time.”

The disease can be treated with a five-day course of antibiotics, she said, and children who are sick should stay home from school while they ate being treated.

Additionally, the Maine CDC recommends pregnant women in their last trimester be vaccinated, as should anyone who will care for an infant, such as a grandparent.

“There’s a risk of fatality with children that small,” Pinette said. “The risk is higher the younger they are.”

BDN writer Jackie Farwell contributed to this report.