Suggest Treatment For Nausea, Dizziness And Vomiting

My father is 62 and we just returned from a cruise that included a few stops in Mexico. A few family members have been sick since returning with vomiting and fever. My father has since been sick for a few days now and his symptoms include nausea, dizziness, and fever and today he had an episode that he thinks he passed out and when he came to he says he didn t know where he was or what he was doing. Also has been very tired feeling.