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BACKGROUND: Mass gatherings can be associated with infectious disease health risks; therefore, surveillance might help early detection and prevention of outbreaks. In 2013, West Virginia hosted for the first time a 10-day camping event that is held by a national youth organization every 4 years. A new mass gathering surveillance system was implemented to detect and prevent outbreaks among the 41,806 attendees. Active surveillance was conducted by a team who performed attendee health screening upon arrival at the site, daily interviews of medical personnel by using standardized questionnaires, and follow-up of disease and outbreak reports. In this study, we assessed the usefulness of the active surveillance system for rapidly detecting outbreaks.
METHODS: We reviewed surveillance data for completeness and timeliness. We assessed the number of outbreaks detected and calculated attack rates within camper groups, which comprised 40 campers each. We administered an Internet-based survey to all medical staff to evaluate their perceptions of active surveillance.
RESULTS: Active surveillance data from medical staff interviews were 100% complete and available for review daily. An outbreak of influenza A was detected among 8 campers in a single group (20% attack rate) and 3 campers from 4 other groups. Gastrointestinal illness was detected among 15 campers in a single group (38% attack rate) and 12 campers from 7 other groups. Of 562 medical staff surveyed, 252 (42%) responded. The majority of respondents reporting interaction with the surveillance team (n = 108) considered information or assistance provided by the team useful (73.1%) and timely (80.8%).
CONCLUSIONS: Active surveillance was useful, enabling detection of 2 outbreaks. Active surveillance should be considered at future outdoor mass gatherings to detect infectious disease outbreaks.