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Pertussis incidence has been increasing since mid-2011 in the state of Washington. The number of cases reported in early 2012 — 2520 — was 1300% higher than the number during the same period in 2011. Rates were highest among infants aged <1 year, children aged 10 years, and adolescents fully vaccinated with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine. Incidence among Hispanics was more than twice that among non-Hispanics (53.1 vs. 24.6 cases per 100,000 population).
A total of 2069 cases were confirmed by laboratory testing (83%) or epidemiologic linking (17%). Multitarget polymerase chain reaction (PCR) assays, performed on 193 specimens in which Bordetella DNA had been detected by PCR, identified B. pe…