Health Advisory: Increase in Pertussis Cases in several Washington Jurisdictions

Edited on May 17, 2024 to update language and include link to a provider alert.

This is a Health Advisory from the Washington State Department of Health (WA DOH) Office of Communicable Disease Epidemiology.

An increase in pertussis has been noted this year in some jurisdictions in Washington State, with a sixfold increase in reported pertussis cases statewide through week 18 (through 5/4/24) compared to cases reported by week 18 last year.  

Actions Requested

  • Be aware of a resurgence in pertussis activity in some areas of the state. Please review the pertussis investigation guideline as needed.
  • Consider informing healthcare providers in your jurisdiction about these increases by sending a provider alert to encourage timely and appropriate testing of potential cases of pertussis.
  • Ensure that clinicians are aware that a negative pertussis PCR or culture result does not rule out pertussis.
  • A nasopharyngeal (NP) swab is the preferred specimen, and PCR is the most sensitive and fastest diagnostic test. Culture is the most specific option, but only about 20% sensitive, and so is rarely done. Note that serology should not be used for diagnosing pertussis cases in Washington.
  • Pertussis testing is usually done commercially but is available at the Public Health Laboratories (PHL) if needed (e.g., for patients with no health care coverage.)
  • Follow up on all reported confirmed and probable pertussis cases to offer prophylaxis to contacts for whom it is indicated. More information about post-exposure prophylaxis is available on pages 12 and 13 of the pertussis guideline.

Current Situation in Washington

A total of 170 confirmed and probable cases have been reported statewide through 5/4/24 (CDC week 18) in 2024, compared to 24 cases reported by week 18 in 2023. Pertussis cases have been reported in 15 counties, with some reporting marked increases.

Number of Pertussis Cases Reported in Washington state by CDC

For more complete information, please refer to the Weekly Pertussis Update. This report is updated each Friday.


Pertussis is a vaccine-preventable bacterial infection that usually causes mild illness in older children and adults but can be life-threatening for infants. Antibiotic therapy can be effective if started early in the course of illness, and postexposure prophylaxis can prevent serious illness in those at increased risk of severe illness. Between 2010 and 2019, the median number of confirmed and probable pertussis cases reported per year was 685.5 cases statewide (mean: 1180 cases per year). A marked decrease in reported pertussis cases was observed in 2020; subsequently, fewer than 100 cases per year were reported during 2021 – 2023. The current increase in activity may represent a resurgence in pertussis.



For questions, or to report suspect cases, please contact: 

Vaccine-Preventable Disease (VPD) Program
Office of Communicable Disease Epidemiology
Washington State Department of Health
Phone: (206) 418-5500

To read this and other WA HAN messages, please visit the Washington Health Alert Network webpage.