Investigation shows a potential exposure source for several cases was whole roasted pigs, cooked and served at private events, said the Washington State Department of Health.
The 56 cases include residents of King (44), Snohomish (4), Mason (2), Thurston (2), Pierce (1), Grays Harbor (1), Yakima (1), and Clark (1) counties, according to data as of July 23. Five people were hospitalized but no deaths have been reported.
The source of contamination is under investigation by state and local health officials and federal partners.
Health officials warn consumers who handle and/or eat pork to cook it to a safe internal temperature, using a meat thermometer; whole cuts of pork should be cooked to 145 degrees.