Vibrio infections and surveillance in Maryland, 2002-2008

Vibrio is a naturally occurring waterborne pathogen with potential occupational, recreational, and commercial impacts. During the last 15 years in the U.S. and in Maryland, the incidence of vibriosis has increased. Due to the increase in cases in Maryland, warming water temperatures, and public concern about human health effects resulting from exposure to the Chesapeake Bay, we reviewed cases of vibriosis and evaluated the Vibrio surveillance system in Maryland for timeliness and data quality, attributes necessary for successful outbreak investigation and illness prevention.

The evaluation included (1) informal qualitative surveys of state and local personnel who report and manage Vibrio cases and (2) a review of Vibrio surveillance data from 2002 through 2008 for data quality and timeliness of the system.

From 2002 to 2008, 188 laboratory-confirmed cases of vibriosis were reported in Maryland with an annual average of 27 cases. The species of Vibrio that were most frequently responsible for infection, regardless of clinical presentation, were V. parahaemolyticus (43.6%), V. vulnificus (23.9%), V. alginolyticus (9.6%), and non-toxigenic V. cholerae (9.0%). The case fatality rate fluctuated during the study period, but the number of cases increased.

The surveillance system in Maryland is flexible and captures cases of vibriosis where specimens were collected for testing; however, the system may not adequately capture mild, self-limiting infections. Better integration of data collection for clinical, laboratory, and environmental information and improved completion of variables for shellfish harvest or water exposure locations could improve the system. Quarterly meetings comprising surveillance, public health laboratory, and food-control personnel could direct and ensure the success of improvement efforts.