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Pertussis, also known as "whooping cough," is a toxin-mediated respiratory illness caused by the bacteria Bordetella pertussis. It is spread primarily by respiratory droplets (droplet spread) produced when an infected person coughs or sneezes. The disease is of particular concern in infants because they have higher rates of pneumonia, hospitalization, and death compared with older children and adults. Pertussis vaccination reduces the frequency and severity of disease.

However, the protective effects of natural pertussis infection and pertussis vaccine wane with time. Unrecognized infections in older children and adults are the most common source of pertussis transmission to infants in the community. The primary strategy to prevent severe pertussis among infants is maternal vaccination during the 3rd trimester of each pregnancy.

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Pertussis clinical information (CDC):


  • Reporting requirements. Health care providers, health care facilities, and laboratories are required to report cases of pertussis in King County residents within 24 hours by calling 206-296-4774.

Purpose of surveillance:

  • To prevent transmission of pertussis to infants and other persons
  • To identify outbreaks and implement disease control measures including vaccination and early recognition, testing, and treatment of cases

Pertussis case data

Local epidemiology:

In 2015, 252 confirmed, probable, and suspect cases of pertussis were reported, compared to a five-year average of 273 cases and to the 2012 outbreak year, when 895 cases were reported. Roughly two-thirds of cases occurred among school-aged children (5-17 years), whereas children under age one accounted for just ten cases. Six cases were hospitalized, including four infants; no deaths were reported.

Eighty-four cases (33%) were determined not to be up-to-date on pertussis-containing vaccine. Vaccination is the best way to prevent pertussis. It is also important to keep infants, pregnant women and other people at high risk for pertussis complications away from infected people.

At least 30 percent of cases were thought to have been exposed at school. Children with pertussis should be diagnosed and treated in a timely manner to prevent exposing other children and high-risk individuals such as pregnant women and immunocompromised individuals.

Typically between 400 and 1,000 pertussis cases are reported each year in Washington state, though 4,920 cases were reported in 2012. Pertussis epidemics follow a cyclical pattern, with peaks every two to five years. Lower numbers of pertussis cases are expected in the years immediately following large outbreaks such as the one Washington state experienced in 2011-12.