Pertussis, the bacteria known as whooping cough, is on the rise again in California.
Santa Clara County has seen fewer infections than Sonoma, Marin and Napa counties this year, with six cases reported in Los Altos, Los Altos Hills and Mountain View as of the first week in July. The California Department of Public Health has tallied nearly 4,600 cases this year – more than all of 2013 – and declared a state of epidemic last month.
Infants face the greatest risks from pertussis infections, and three have died in California this year. Children younger than 5 months account for nearly two-thirds of pertussis hospitalizations. Many adults may not realize that their simple cough, lingering for weeks, stems from a pertussis infection. The illness presents with a lingering cough, which often causes a violent “whooping” noise in children. Pertussis can cause fatal breathing difficulties for babies, who often show no coughing symptoms at all.
The Department of Public Health encourages pregnant women to get vaccinated – even if their shots are up to date – because a third-trimester jab can offer particular immunity for the baby after birth.
“Inoculated women pass the immunity to their unborn babies. It can protect them until they can be vaccinated. Infants should be vaccinated as soon as possible,” Dr. Ron Chapman, director of the California Department of Public Health, wrote in a recent announcement. “The first dose of pertussis vaccine can be given as early as 6 weeks of age.”
Of the 43 infant cases of pertussis this year for which the Department of Public Health could get a vaccination history, seven mothers had received the pertussis, tetanus and diphtheria vaccine, known as the DTaP, during pregnancy, most of them not during the third trimester.
Most of the older children contracting pertussis in California this year had a history of vaccination – only 9 percent of reported cases for which vaccination history was available had never received the vaccine.
Because immunity to the DTaP vaccine fades over time, children and adults who will be spending time around newborns often need a new vaccination, regardless of whether they have had the illness or an earlier vaccination.
Ross DeHovitz, M.D., a pediatrician with the Palo Alto Medical Foundation, explained that pertussis appears to come in waves every three to five years, perhaps as it moves through a population and people begin to gain immunity and temporarily slow the epidemic’s spread.
“I don’t think we really understand all the reasons for that, but we know the vaccine is not perfect – it doesn’t last very long when you give it to adults,” he said, explaining some of the best guesses as to why the bacteria returns cyclically.
Once diagnosed with pertussis, patients can take an antibiotic to limit their infectiousness, but it doesn’t appear to abbreviate the course of illness or its lingering cough, DeHovitz said.
“Pertussis creates a level of inflammation in your lungs that creates mucus and irritation and sets off the cough reflex,” he said. “Sometimes inflammation lasts so long that you may be coughing well after the presence of the bacteria (has gone).”
Adults find the lingering irritation more nuisance than danger, but babies can respond to the inflammation with apnea – cessation of breathing – and risk pneumonia, seizures or brain damage.
“Vaccination is only one part of this, but it is an important part of it,” DeHovitz said. “It’s a new idea to vaccinate pregnant women (against pertussis), but it has been shown to be safe and effective. People should understand that it is OK to be hesitant, but the data seem very reassuring. We’re trying to get the baby immunized from the very beginning.”