Dr. Samuel Mathis, assistant professor in the University of Texas Medical Branch Department of Family Medicine, said the resilient virus can live for days and there are plenty of places for it to linger on cruise ships. Mathis, who works in Galveston, cruise port, has seen passengers with norovirus. He said that while the virus itself is uncomfortable, it isn’t typically dangerous. “The biggest risk for almost everyone — but especially for seniors — is actually the risk of dehydration: losing all that fluid through nausea, vomiting and diarrhea.”