County’s pertussis rate is highest in state

There’s an outbreak of the respiratory infection Enterovirus 68 in the Midwest, and the continuing spread of Ebola from West Africa. But here in Sonoma County, health officials have their own worries: the high incidence of pertussis, or whooping cough.

Building on a surge of 50 additional cases per week in the spring months, Sonoma County jumped to an early lead in California by a wide margin in the rate of pertussis cases this year, a dubious honor it continues to hold. Although the vaccination rate in Sonoma Valley is among the best in the county, with most schools close to or above the desired threshold of 95 percent inoculation, local health officials are steadfast in reminding residents of the importance of being vaccinated.

Though she could not give specific figures, Kathy Mathews, clinical quality coordinator for infection prevention and risk management at Sonoma Valley Hospital, confirms that officials have seen more cases of pertussis than in previous years, “consistent with the reports we’re getting from the Public Health Department that the county has experienced an outbreak in 2014.”

The most recent report from the California Department of Public Health, released Sept. 15, shows 8,278 cases in the state, with 679 of them in Sonoma County, leading to five hospitalizations but no deaths. Larger counties have had more cases by number, but the incidence rate in Sonoma tops the list at almost 138 cases per 100,000 persons, compared to 21.7 per 100,000 statewide.

Neighboring counties Napa and Marin have the next-highest pertussis rates in the state, though neither top the 100-per-100,000 threshold. The locally high rates of pertussis do not escape Dr. Karen Holbrook, deputy health officer for the county’s Department of Health Services. “That’s how it spreads, person to person, and our populations between counties do intermix,” she said.

While pertussis is rarely fatal, it can be a distressing illness for the very young or the very old. Infants and young children may show signs at first much like a common cold, with a runny nose, cough and slightly elevated temperature. But if not identified and treated quickly, that cough can become persistent and wracking, and last up to 100 days.

“It’s important in the first two weeks of the disease that they get treatment, because you’re highly contagious in the first two weeks,” warned Mathews.

Current lab testing for the disease is fast and accurate. If there’s been a reported case in the child’s school – all cases are reported to the county health department, which in turn requires schools to alert their students’ parents – then any child with a cold should be tested for pertussis, she emphasized.

It’s not just the high incidence of pertussis that has health officials concerned: a significant number of parents are refusing to vaccinate their school-age children against this and other preventable diseases, claiming a “personal belief exemption,” or PBE, that only 19 of the 50 states allow.

A parent can chose a PBE for almost any reason; but doctors privately fear too many parents accept unreliable and disproven claims that autism, epilepsy and other troubles can be caused by vaccinations.

Since 1962, California has required children starting kindergarten to have certain vaccinations, including for whooping cough. Recently, students entering seventh grade are also required to have an up-to-date Tdap vaccination which covers tetanus, diphtheria and pertussis.

Prior to this year, the PBE was simply a matter of a parent signing off without consulting a physician. But that law changed on the first of the year, as AB 2109 now requires that the parent must sit down with a medical provider and go over the risks that skipping immunization brings – not only to the individual but to the school and community. Now, too, a medical provider must co-sign the PBE request to validate it.

Holbrook believes, however, that much of the rise in pertussis can be attributed to waning immunity, not PBEs. “The highest numbers of cases, about 70 percent, were among children aged 10 to 18. This is likely an effect of waning immunity,” she said, since the acellular pertussis vaccine currently in use is not as effective or as long-lasting as the older immunization. She adds, “It is true that the majority of cases for whom vaccination history is known are vaccinated.”

But Holbrook remains concerned about the high rates of exemptions too. “It poses a risk to the individual and those around them,” she said. The side effects of refusing vaccination are cause for concern, since so-called “herd immunity” holds that for a population to be resistant to widespread outbreaks of diseases like pertussis, at least 90 percent and preferably 95 percent or more should be immunized.