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Public Health - Seattle & King County


Measles is one of the most highly contagious diseases, but is preventable through vaccination. The measles virus is spread through coughing and sneezing. Before widespread use of measles vaccines there was an average of half a million measles cases and hundreds of deaths each year in the United States. Measles is common in many parts of the world, including both industrialized and developing countries. Local cases of measles are often linked to travel or exposure to recent travelers. Worldwide, more than 20 million people are infected each year. Measles is the leading cause of vaccine-preventable death among children in the world.

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Measles in King County

Purpose of surveillance:

  • To facilitate prompt diagnostic testing
  • To identify cases and exposed persons at risk for transmitting measles to others
  • To identify susceptible contacts of cases for post-exposure prophylaxis or preventive treatment
  • To implement disease control measures to prevent transmission

Measles Case Data in King County

Local epidemiology:

In 2014, an outbreak of 16 measles cases, including 13 from King County, affected a local community of residents from the Federated States of Micronesia, to which the index case had recently traveled. Cases occurred from late May to early July. Four of the cases were exposed to the virus in healthcare settings. A majority of the outbreak-associated cases were either unvaccinated or too young to be vaccinated against measles. Community clinics were held by Public Health to provide MMR vaccine to members of the community with undocumented immunity to measles.

In recent years, all measles cases in King County have been imported from other countries or linked to an imported case.

Most years in Washington state fewer than 10 measles cases are reported; the last large outbreak occurred in 2008 with 19 reported cases.

Immunization levels at King County schools

Look up immunization levels at King County schools on an interactive map

Questions and answers about measles for childcares and schools