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November 19, 2024

Pertussis cases continue to increase in King County

Actions requested

Be aware of a substantial increase in reported pertussis cases in King County and across Washington state.

  • Identify

    • Consider pertussis in people with:
      • Respiratory symptoms, especially in infants <12 months, when accompanied by difficulty feeding or apnea.
      • Cough illness, in patients of any age, characterized by one or more of:
        • Paroxysmal cough
        • Gagging, post-tussive emesis, or inspiratory whoop
        • Lasting 2 weeks or longer
      • Respiratory illness of any duration in patients who had contact with someone with pertussis or pertussis-like symptoms.

  • Test

    • Collect nasopharyngeal (NP) swab for pertussis PCR or culture.
      • Do NOT use serology to diagnose pertussis (less reliable for acute infections).
    • A negative pertussis PCR or culture does not rule out pertussis.

  • Manage

    • Patient Treatment: Follow CDC guidance for suspected or lab-confirmed pertussis.
    • Patient Education: Exclude them from work, school, or childcare until after completing 5 days of appropriate antibiotic treatment.
      • Advise them they are contagious from symptom onset through 21 days after paroxysmal cough onset OR until they have completed 5 full days of appropriate antibiotics.
    • Contact Treatment: Consider post-exposure prophylaxis (PEP) within 21 days of exposure for household contacts and for contacts who are high-risk either for severe disease or for having close contact with high-risk people, including:
      • Infants <1 year old (who are at greatest risk for severe disease and death)
      • Pregnant people in the last trimester (who will expose newborn infants)
      • People with pre-existing health conditions that may be exacerbated by pertussis
      • Healthcare workers with direct patient contact
      • People who come into direct contact with infants <1 year old or pregnant people (e.g., childbirth educators, childcare staff, members of household with an infant)

  • Notify

    Report suspected and confirmed pertussis cases to Public Health at 206-296-4774 within 24 hours.

  • Vaccinate

Background

Pertussis rates were lower during the COVID-19 pandemic but rates in the U.S. are beginning to return to pre-pandemic levels. During January–October, 2024, 154 pertussis cases were reported in King County compared to 126 cases total during 2019–2023. Washington State has seen a 21-fold increase in pertussis cases reported statewide compared to last year. Roughly half (44%) of King County pertussis cases reported in 2024 have been among infants and children under 6 years old, including several infants who required hospitalization. Of the 14 pertussis cases in infants reported in King County in 2024, only one birth parent received the recommended Tdap during their pregnancy.

Pertussis is a highly contagious vaccine-preventable disease, typically starting with cold-like symptoms that develop into a worsening cough illness lasting several weeks, highlighted by paroxysms, post-tussive vomiting, inspiratory whoop, apnea, and cyanosis. Depending on prior exposure and vaccination history, older children, adolescents, and adults may present with milder symptoms, but can still transmit pertussis to close contacts. Severe and sometimes fatal pertussis-related complications can occur in infants under 12 months of age, especially those under 4 months of age. Identification of pertussis and prompt treatment reduces the contagious period and risk of further transmission. We recommend all household members and other close contacts receive PEP.

Vaccination for pertussis is recommended for persons of all ages in the U.S. and is critical to prevent severe illness in infants and young children. Only 80% of 2-year-olds in King County have received the recommended 4 doses of DTaP, which is well below the target rate of 90%. Vaccination of pregnant people is important to protect newborns and infants, and healthcare providers should strongly recommend and offer Tdap vaccination to pregnant people in the third trimester of each pregnancy regardless of prior vaccination history.

Resources

This health advisory is also available in PDF format (226 KB)

For healthcare providers

For infection preventionists

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