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Prions are infectious proteins that cause illness when they fold abnormally in the brain. These illnesses are sometimes called transmissible spongiform encephalopathies (TSE). The most common human prion disease is Creutzfeldt-Jakob Disease (CJD), a rare, rapidly progressive neurodegenerative disorder. CJD is always fatal, typically causing death within a year of onset. Classic CJD has been recognized since the early 1920s. Most CJD cases are sporadic (85%), and some are familial (15%). The diagnosis is confirmed by laboratory tests on brain tissue obtained by biopsy or autopsy. In recent years, the United States has reported fewer than 300 cases of CJD a year.
In 1996, a new type of CJD called "variant" CJD (or vCJD) was recognized in the United Kingdom. This type is associated with Bovine Spongiform Encephalopathy (BSE), a neurodegenerative disorder in cattle also called "mad cow disease."

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Prion diseases in King County

Purpose of surveillance:

  • To detect cases of rare and emerging diseases
  • To understand the epidemiology of rare and emerging diseases
  • To identify potentially exposed persons

Local epidemiology:

Three cases of prion disease were reported in 2015.

  2011 2012 2013 2014 2015 Grand Total
Familial CJD   2 1     3
Sporadic CJD 1 3 5 2 3 14
Grant Total 1 5 6 2 3 17

Each year in Washington state between seven and 17 CJD cases are reported.

Just four vCJD cases have ever been identified in residents of the United States (last known case in 2014). All were likely exposed through eating cattle products outside the United States, in the United Kingdom (two cases) and Saudi Arabia (one case).