sentence1: Approximately a dozen individuals have reported becoming sick after eating raw oysters consumed in a restaurant in Chattanooga, Tennessee. The Chattanooga-Hamilton County Health Department and Tennessee Department of Health confirmed that the patients were infected with norovirus.  Norovirus is a foodborne pathogen that can cause acute gastroenteritis in humans. The symptoms of norovirus illness begin suddenly, most often in 24 to 48 hours after ingestion of the virus, but they can appear as early as 12 hours after exposure. The gastrointestinal symptoms include nausea, vomiting, diarrhea, and some stomach cramping.
sentence2: Oysters have been linked to gastrointestinal diseases caused by a virus.