"The outbreaks are in high schools and middle schools," Holbrook said, adding that a number of other schools are reporting confirmed cases but only six schools have outbreaks so far.
The county has launched a public health campaign urging parents to vaccinate children and infants and to keep current on vaccination schedules. Infants younger than 6 months old are the most likely to suffer complications from whooping cough, which include pneumonia and even death.
In 2010, 10 infants died across the state. This year, in Sonoma County there has been only one hospitalization. No deaths have been reported locally.
The county-wide campaign also urges local parents and family physicians to be vigilant of the tell-tale signs of pertussis — a persistent cough that often ends with a high pitched "whooping" sound and even vomiting. If such symptoms exist, Holbrook said doctors should immediately put the patient on antibiotics.
"Doctors should treat suspect cases and not wait for confirmation to come back," Holbrook said.
The pertussis bacteria is primarily spread through the air by droplets from coughing or sneezing. The incubation period is seven to 10 days. The first stage of symptoms lasts between one and two weeks and includes runny nose, sneezing and a mild cough.
The next stage is characterized by persistent coughing that can sometimes go on for several minutes until the air is gone from the lungs and a person is forced to inhale with a loud "whooping" sound. Sometimes a patient can turn blue during coughing fits, and vomiting and exhaustion commonly follow an episode.
Recovery is gradual during the final convalescent stage, which often lasts up to six weeks. But according to the federal Centers for Disease Control and Prevention, coughing fits can recur with subsequent respiratory infections for many months after the onset of pertussis.
William Brady of Petaluma noticed whooping cough symptoms in his granddaughter recently while picking her up from Petaluma Junior High School.
"Every day I picked her up she was coughing worse," he said, adding that she was diagnosed with pertussis and put on antibiotics last week.
"She had an episode two days ago where she coughs so hard she vomits," he said, adding that she's had the symptoms for three weeks.
On Wednesday, Brady's family received notice that there have been several cases of whooping cough at Petaluma Junior High School.
In Santa Rosa City Schools, Sonoma County's largest school district, there have been approximately five confirmed cases, according to Superintendent Socorro Shiels, after which officials sent out letters to all parents and made automatic calls home. Communication has gone out in both English and Spanish
.
"Definitely in the last month, we are much more aware of whooping cough," Shiels said.
Santa Rosa High School had a confirmed case in late February.
Schools, where students spend the day in close proximity with one another and don't always practice good hygiene, can be breeding grounds for illness. But schools can also be a key component in communicating information on symptoms and treatment to families that may include vulnerable populations like pregnant woman and small children, Shiels said.
"I hope we can serve as that conduit for public service announcements," she said.
At some schools, additional signs have been posted urging hand washing and covered mouths.
Petaluma Junior High has had two or three cases since the first confirmed case was reported nearly two months ago, said Principal Renee Semik. The school had a very high rate of vaccination this year, she said.
Following Petaluma City Schools protocol, an information email in both English and Spanish, was sent to parents, followed by a hard copy letter. A follow-up email about symptoms and information on who is most at risk was sent this week.
"They are trying to keep staff, students with an understanding of what to look for," Semik said.
If students have symptoms associated with whooping cough, Semik has asked parents to keep them home.
"We need you to take a look at it, take care of it," she said.
Holbrook said the best prevention against the disease is "vaccination and good infection control."
But Holbrook said vaccination against pertussis is not "100 percent effective" and immunity wanes over time. Unlike the measles, immunity is not acquired through vaccination or by contracting the disease.
Of the 121 cases this year, 88 percent were up to date on their vaccinations; 8 percent were unvaccinated and 3 to 4 percent were cases where the vaccination status was unknown.
But Holbrook warned that such statistics should not be construed as an example of the ineffectiveness of the vaccines.
"People forget how common and deadly these illnesses are," Holbrook said. "Despite the waning immunity, vaccinations still prevent lots of disease. Vaccination is still the best way to prevent illness."
During the pre-vaccine era — from 1940 to 1948 — pertussis caused more deaths in the United States among children during their first year of life than measles, meningitis, scarlet fever, diphtheria and poliomyelitis combined, Holbrook said.
Of the 121 confirmed pertussis cases this year, only 4 percent are children 4 and under, the group that is most prone to suffer the most severe medical complications.
For that reason, the main focus of the county's public health campaign is protecting the area's youngest residents.
The CDC recommends the following measures be taken:
--Pregnant women be vaccinated in their third trimester to build maternal antibodies that are transferred to the baby.
--Once a child is born, all family members and care-givers should be vaccinated, a strategy known as cocooning.
--Make sure infants get a full schedule of pertussis vaccinations, as recommended by the CDC.
Health officials recommend giving children five doses of DTaP vaccine at 2, 4, 6 and 15 to 18 months and between 4 and 6 years. A final whooping cough booster Tdap is required for seventh- through 12th-graders, though parents can opt out with a "personal belief exemption" waiver.
"We are focusing on those most vulnerable," Holbrook said. "We're getting the word out to clinicians and hopefully parents and pregnant women. It's really important that they be immunized."
Back in mid-March — when there were only 35 confirmed cases in the county — the public health department sent out a health advisory warning local physicians that a trend was taking place.
After dropping significantly following the recent peak in 2010, the number of pertussis more than doubled from 20 cases in 2012 to 46 in 2013.
The trend was happening and I wanted our physicians to know about it," Holbrook said.
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