PORT TOWNSEND — No sooner does the threat of measles in Clallam County fade than cases of whooping cough shoot up in neighboring Jefferson County.
Pertussis, which causes severe coughing that accounts for its common name, likely is on its way across the North Olympic Peninsula, health officials say.
As of mid-April, 17 cases of whooping cough had been reported in Jefferson County among its 29,300 people, said Dr. Tom Locke, county health officer, on Friday.
On April 11, the state Department of Health reported 11 cases in Jefferson County. That made the county second in the state per capita, with a rate of 37.5 out of 100,000 people.
It was just behind Walla Walla County, which had 28 cases reported for a rate of 47 out of 100,000.
Other leading counties in terms of total cases included Kitsap (85), King (41), Clark (39), Pierce (30) and Snohomish (28).
The contagion period for the most recent case among five linked diagnoses of measles in Clallam County ends today.
The first case was diagnosed Feb. 1. No cases were confirmed in Jefferson County.
Measles is the most contagious viral disease known to doctors, Locke said, while pertussis holds that distinction among bacterial infections.
“If people are susceptible, they have a very high probability of getting it,” he said.
As with measles, whooping cough is largely preventable through vaccinations and is thought of as a childhood disease, though it has deadly outcomes among infants.
Both Jefferson and Clallam counties lag in the percentage of youngsters who have immunity to tetanus, diphtheria and pertussis (DTaP vaccine for children, Tdap shots for adolescents and adults).
According to the latest figures available from the state health department, Port Townsend schools had a 10.5 percent exemption rate — mostly for personal reasons— from DTaP and Tdap vaccinations in 2014.
In Port Angeles, 4.1 percent of students were exempt.
Exemption rates for tetanus, diphtheria and pertussis in other North Olympic Peninsula districts:
■ Brinnon, Chimacum: Both 8.6 percent.
■ Cape Flattery: 2.6 percent.
■ Crescent: 9.9 percent.
■ Quilcene: 2.9 percent.
■ Quillayute Valley: 0.9 percent.
■ Sequim: 7 percent.
Pertussis can be deadly to infants and young children, as well as to elders and people with damaged immune systems.
Pregnant women especially should get vaccinated, Locke said, and be revaccinated every time they become pregnant.
The vaccine’s antibodies are transmitted to the developing fetus, Locke said, and the repeated vaccinations build the mother’s immunity.
In our region, Locke said, the pertussis outbreak started in Kitsap County, spread to Jefferson and will come to Clallam, which as of Friday had reported no cases.
Pertussis rears up in three- to four-year cycles, he said.
Although there are vaccines against the illness, “a reservoir of mild pertussis” lingers in the adolescent and adult populations, and breaks out roughly with the same frequency as measles.
Pertussis spreads through droplets sneezed or coughed by sufferers that others can inhale from up to 3 feet away.
Pertussis germs also linger on surfaces.
These characteristics make it important to cover coughs and wash hands frequently, Locke said.
The vaccine doesn’t offer perfect protection against pertussis — only about 70 percent, according to the federal Centers for Disease Control and Prevention — but it drastically reduces symptoms and the danger of death in people who catch it, he said.
It’s a relatively mild ailment for adults, although it’s renowned for its trademark cough.
“Even if you’re not ‘whooping,’ everyone who has pertussis has one of the most severe coughs they can remember,” Locke said.
“You can cough for months after a case of pertussis.”
Because it is a “notifiable condition,” county health departments learn of each case of pertussis, find out whom sufferers have contacted and treat sufferers and, in some cases, their contacts with antibiotics.
Antibiotic drugs reduce a patient’s period of contagiousness from 21 to five days, Locke said.
Most of the Jefferson County cases have been among elementary, middle and high school students, he said, but health officials’ emphasis is on infants and pregnant women because newborns and infants younger than 6 weeks old suffer the highest percentage of fatalities from pertussis.
Other elements in Jefferson County’s pertussis education program include teaching the “respiratory hygiene” of covering one’s cough, washing one’s hands and staying home if sick; encouraging vaccinations; and protecting at-risk people.
Vaccination targets include caretakers of infants and young children.
“Parents, baby-sitters, grandparents — anybody who’s going to be around an infant — should be vaccinated for pertussis,” Locke said.
Although no cases had been reported in Clallam County as last week ended, Dr. Jeanette Stehr-Green, health officer, had sent “a blast fax to all of our providers outlining pertussis, what to look for and how to treat it,” said Iva Burks, county Health and Human Services director.
Burks urged parents to check their vaccination records and said people with infants should have them vaccinated as soon as possible.
“We don’t want to lose any babies to pertussis, for heaven’s sake,” she said.
Pertussis wasn’t epidemic during the past few years. Clallam County reported 20 cases to the Department of Health in 2014; Jefferson county had one case. In 2013, Clallam County had 13 cases, and Jefferson reported none.
But in 2012, pertussis cases totaled 25 in each county, while cases across the state spiked at 2,520 in June of that year and eventually reached 4,916.
So far this year, the state has received reports of 319 cases compared with 49 in 2014.
With whooping cough making a comeback on the heels of a measles outbreak, “it looks like it’s going to be a bad year,” Locke said, “at least from a human standpoint.
“From the microbe standpoint, they’re having a grand old time.”
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Reporter James Casey can be reached at 360-452-2345, ext. 5074, or at jcasey@peninsuladailynews.com.