April 20, 2024

Increase in pertussis cases in King County

Actions requested

Be aware of an 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. Treatment should occur during the first 1 to 2 weeks before coughing paroxysms occur.
Patient Education: Instruct them to stay home from work, school, or childcare. Advise them they are contagious until they have completed 5 full days of appropriate antibiotics.
Contact Treatment: Consider post-exposure prophylaxis (PEP) antibiotics 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 persons 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

All children and adults should be up to date on recommended pertussis vaccines.

Pregnant people should receive 1 dose of Tdap during each pregnancy at 27-36 weeks gestation (third trimester).

Assess immunization status of patients at every visit and strongly recommend vaccination based on recommended schedule, health condition, occupation, and other risk factors.

CONTACT

Communicable Diseases Epidemiology and Immunization Section

401 5th Ave, Suite 1250
Seattle, WA 98104

Phone: 206-296-4774
TTY Relay: 711

Fax: 206-296-4803

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Background

Pertussis rates were lower during the COVID-19 pandemic but rates in the U.S. are beginning to return to pre-pandemic levels. Pertussis cases reported through May 2024 have already exceeded the combined annual totals from 2022 and 2023 for both King County and Washington State. Roughly half of King County pertussis cases reported in 2024 have been among infants and children <5 years old, including several infants who required hospitalization. Of the 9 pertussis cases in King county infants reported in 2024, none of their birth parents 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.

People with pertussis are infectious from onset until at least three weeks after paroxysms begin or after 5 full days of appropriate antibiotics. Identification of pertussis cases and prompt antibiotic treatment reduces the contagious period and risk of further transmission. It is recommended that all household members and other close contacts receive PEP antibiotics.

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 79% 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.