Vibrio species are bacteria that occur naturally in marine waters. Eating undercooked or raw shellfish, especially raw oysters, is the main risk for acquiring vibriosis due to infection with Vibrio parahaemolyticus. Growth of Vibrio species in seawater is amplified during the warm months and Vibrio levels in shellfish increase during the summer. Vibrio cholera causes potentially severe diarrhea that does not occur naturally in the United States.
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Purpose of surveillance:
- To identify common source outbreaks
- To identify and eliminate sources of transmission including contaminated food and water
Twenty-seven cases of vibriosis were reported in 2012. One of the cases required hospitalization, none died. Twenty-four of the cases were due to V. parahaemolyticus, one was V. alginolyticus, one was non-toxigenic V. cholerae, and one was caused by Grimontia hollisae (closely related bacteria which cause Vibrio-like illness).
Twenty of the twenty five V. parahaemolyticus or G. hollisae cases reported oyster consumption during their exposure period; eighteen cases ate the oysters raw. Fifteen cases purchased their oysters from King County commercial food establishments, three purchased from vendors outside of King County, and two harvested their oysters recreationally. One case was exposed while traveling in Mexico, and three cases were unable to be reached for interview.
The V. alginolyticus case presented with an ear infection after swimming off the Florida coast. The person infected with non-toxigenic V. cholera was exposed while traveling in Asia and had consumed several types of seafood.
The last large local outbreak of vibriosis occurred in 2006, when 50 cases of vibriosis (39 laboratory-confirmed and 11 probable) were reported in King County residents.
Over the last ten years in Washington state, between 18 and 80 cases have been reported, with the number varying depending on environmental conditions.