Sunday, March 9, 2014
The worst year since at least the 1960s for whooping cough cases in Maine started out slowly.
Susan Huff, a Portland Community Health Center medical assistant, administers a pertussis vaccine to colleague Brianna Gonthier. Adults should get a booster shot every 10 years.
John Patriquin/Staff Photographer
While the first half of 2012 saw just a handful of cases, according to statistics released by the Maine Center for Disease Control and Prevention, reports of pertussis began to pick up by May and mushroomed during the summer and early fall before falling back in mid-October.
Whether 2013 will have an outbreak as severe as last year's is still in question, officials said. The 2013 numbers are so far tracking in a similar manner to 2012, but the bulk of last year's surge happened in midsummer and early fall. Unlike influenza, which peaks in the winter, pertussis outbreaks can happen during any season, officials said.
Maine ended 2012 with 737 reported cases of pertussis, giving it the seventh-highest per capita rate in the nation, according to the U.S. Centers for Disease Control and Prevention. Most happened in the last six months of the year.
If the second half of 2012 had been similar to the first half, Maine would have finished with about 300 cases instead of 737.
"It's unpredictable," said Sheila Pinette, executive director of the Maine CDC. "We don't know when or where it will happen."
Nationally, whooping cough has surged back after decades of being almost eradicated from the infectious-disease landscape.
Before the whooping cough vaccine became available in the late 1940s, hundreds of thousands of cases were reported annually.
Pertussis cases plunged to a few thousand per year in the 1970s and 1980s, but the numbers are now rising, although not to 1940s levels. About 41,000 pertussis cases were reported nationally in 2012.
EXPLAINING THE OUTBREAK DIFFICULT
In Maine, the specifics of how the 2012 outbreak happened and why some counties were hit hard while others saw few cases are unknown, officials said.
For instance, Somerset County experienced 102 cases in 2012, the highest per-capita rate in the state. But only one case surfaced in neighboring Franklin County. In Cumberland County, 225 residents suffered from pertussis, the fourth-highest rate in the state, but neighboring York County had only 70 cases, where the per-capita rate was far below the state average.
"We know where it was," said Dr. Stephen Sears, the state epidemiologist. "We don't know why."
Not only was the geographic distribution of pertussis uneven, but the timing of the outbreak varied from county to county, officials said.
For instance, Cumberland County's outbreak peaked in August and September, with 86 cases in two months. Meanwhile, Somerset County's pertussis cases skyrocketed in May and June, when 56 of its 102 cases occurred. But pertussis petered out in Somerset County by early August, according to state records.
Even why the outbreak happened at all is not clear, but Sears and Pinette have some theories. Maine's population swells in the summer tourist season, which means different populations of people are intermingling at higher densities, Pinette said, making it more likely that infectious diseases will spread.
Whooping cough can last 90 days or longer, and can be lethal for infants. It's most contagious a few days before symptoms appear and the first week after symptoms begin, officials said.
Sears said summer camps and the start of school also expose students to more dense and different populations. In Cumberland County, 49 cases occurred between Aug. 20 and Sept. 20. Sears said summer camps are probably not as much of a factor as school, because of the longer time periods that students spend indoors at school.
Mary Deschenes, executive director of the Maine Youth Camping Foundation, said camps, like schools, promote vaccines but do not require children to be immunized. But most camps do require records of vaccinations. "That way, we know who's immunized and who isn't," Deschenes said. She said most camps will also call the families a few days before the start of camp to ask about any health problems with the child or family members.
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