In May 2012 an outbreak of norovirus occurred among attendees of a dinner gala at Griffin Mansions located in Las Vegas, Nevada. The source of the infection was not identified but the investigation revealed an unlicensed kitchen and a domestic well that might have provided contaminated potable water. Of the 108 attendees included in the public health investigation, 51 (47%) reported illness consistent with a primary case definition. Additionally 12 persons reported illness consistent with a secondary infection.