Multistate outbreak of norovirus gastroenteritis among attendees at a family reunion--Grant County, West Virginia, October 2006.

On October 17, 2006, the West Virginia Department of Health and Human Resources (WVDHHR) was notified of an outbreak of acute gastroenteritis, characterized by vomiting and diarrhea, among attendees at a family reunion. The outbreak initially was reported by a group of attendees to their local health department in Garrett County, Maryland. The same day, the information was relayed to the Grant County Health Department in West Virginia and subsequently to WVDHHR. The reunion was held on October 14 at a private residence in Grant County, West Virginia, and the 53 identified attendees included residents from Florida, Maryland, New York, Pennsylvania, Virginia, and West Virginia. This report describes a collaborative, multijurisdictional epidemiologic investigation using a cohort study and laboratory analyses to determine the source of infection and appropriate control measures. The results indicated that a combination of person-to-person and foodborne transmission of two strains of norovirus, likely introduced by persons from two different states and subsequently at least two food items, was the probable cause of these illnesses, highlighting the challenge of investigating and controlling norovirus outbreaks. During periods of peak norovirus activity, public health officials should emphasize the importance of appropriate handwashing and the exclusion of ill persons from social gatherings.