The illnesses were first noted when officials received calls about a dozen sick people Thursday evening at Reagan National Airport. The travelers had similar symptoms, including nausea, said Rob Yingling, spokesman for the Metropolitan Washington Airports Authority.
Noroviruses cause the stomach flu, also known as gastroenteritis, the health department said. People can get it through contact with infected people, ingesting contaminated food or drink, or by touching contaminated items and then their mouths.
About 350 people attended the conference, and all but one of the 65 people who became ill have returned home, health officials said. The specific focus of the convention was unclear.
Staff members of the Prince George's County health department interviewed resort workers and inspected the center to determine what caused the illness. A private company has already started cleaning, health officials said.
Noroviruses have been responsible in recent years for sickening hundreds of passengers on cruise ships.