Cases of whooping cough in Maine have more than quadrupled in the past year, mirroring a trend that has the United States headed for its worst year of whooping cough in more than 50 years.

In Maine and across the country, large numbers of cases are being seen in adolescents who may be overdue for a vaccine booster. The increase has prompted federal health officials to investigate its cause and the effectiveness of vaccines.

Federal health officials see better detection and more reporting of pertussis as factors in the increase.

The Maine Center for Disease Control and Prevention reported 347 confirmed or probable cases of whooping cough statewide through Aug. 9 this year, compared with 79 cases during the same period last year. This year’s cases include 99 in Cumberland County, 85 in Somerset County and 47 in Penobscot County.

Nationally, more than 21,000 cases of pertussis — and nine related deaths — have been reported this year, according to the national Centers for Disease Control and Prevention. There were 15,216 reported cases in all of 2011 and 27,550 cases in 2010.

To date, 37 states have reported increases in whooping cough over the same period in 2011. A whooping cough epidemic was declared in Washington state, where nearly 3,500 people have been diagnosed this year, more than three times the number for 2011.

Most cases in Maine have been in children ages 7 to 19, though cases in adults are also on the rise, said Dr. Sheila Pinette, director of the Maine CDC. The CDC has been notified of 16 cases in adults in their 30s and 17 cases in adults in their 40s.

Whooping cough is a highly communicable respiratory disease that causes long coughing fits and is characterized by a “whooping” sound as a person gasps for air. Coughing fits caused by pertussis infection usually last one to six weeks, but can go on longer. It can be a life-threatening disease for babies.

The high rate of whooping cough among teenagers in Maine reflects a national trend and may indicate early waning of vaccines, say federal health officials. It also indicates that teenagers and adults are not being immunized, Pinette said.

Children are typically vaccinated for whooping cough as part of a series of immunizations, but the vaccine loses effectiveness over time. Unvaccinated children are eight times as likely to become infected with pertussis. Vaccinated children who get pertussis have milder symptoms and recover faster, according to the CDC.

Health officials expect to see peaks in whooping cough every three to five years, as well as frequent outbreaks. This year’s dramatic increase — especially among adolescents — prompted federal health officials to look into the cause.

Tami Skoff, an epidemiologist with the national CDC in Atlanta, said health officials attribute the rise in part to more reporting of cases by doctors and improvements in lab tests for whooping cough. They also are looking at the length of vaccines’ effectiveness.

The vaccine that children got for many years was replaced in the 1990s because of concerns about side effects. The new version is considered safer but may not be as effective in the long term, Skoff said.

The government recommends that children get vaccinated in five shots between the age of 2 months and 6 years. A tetanus, diphtheria, pertussis booster shot is recommended around age 11 or 12.

Doctors also recommend that adults who have not had the booster receive a one-time dose, especially if they have close contact with an infant.

“We’re most concerned when young infants get the disease,” Skoff said. “This is the age group where we have pertussis deaths.”

Officials say they don’t believe the increase in cases is being driven by children whose parents choose not to have them vaccinated. Some parents don’t have their children vaccinated against common illnesses because of concerns about vaccines, essentially relying on others to be vaccinated to prevent the spread of diseases.

In Maine, more than 90 percent of children receive vaccines. The immunization rate for whooping cough drops to 70 percent for children ages 11 to 19, Pinette said.

“Even if they have had at least one vaccine, their immunity starts to wax and wane over time,” she said. “It puts those children who are not immunized at risk.”

Children tend to spread whooping cough in school because they are together, Pinette said. School officials in Scarborough notified parents of four whooping cough cases in the spring, and eight cases were reported among children in Skowhegan.

School departments are educating their staffs about symptoms and emphasizing to students the importance of good hygiene.

Westbrook schools have not had any confirmed cases in recent years, but school officials keep an eye on warnings from the CDC, said Superintendent Marc Gousse. Teachers will be given information about whooping cough symptoms before the new school year begins, he said.

In Falmouth, school nurses will provide staff members with information about the disease and encourage them to watch for students showing symptoms.

Sue Raatikainen, the nurse at Falmouth Elementary School, said the staff also will talk to students about covering their coughs and washing their hands properly to prevent the spread of illness.

“We’re recommending students get updated on their (tetanus, diphtheria, pertussis vaccine),” she said. “I would encourage parents not to be overly concerned, but it’s certainly important to be aware.”

Dr. Jonathan Sanburg, a pediatrician and adolescent-medicine specialist at South Portland Pediatrics, said he has seen more parents asking about the disease and vaccinations. His practice has treated a couple of whooping cough cases this year, and tested many other patients who have come in with persistent coughs.

“I certainly see an increased awareness of the disease,” he said. “When kids come in with a cough, parents ask about (whooping cough).”

Skoff, the epidemiologist with the national CDC, said the best thing people can do to prevent whooping cough is stay up to date on vaccinations.

“This disease is here,” Skoff said. “It is not going away.” 

Staff Writer Gillian Graham can be contacted at 791-6315 or at:

[email protected]oday.com

Twitter: grahamgillian