sometimes it starts with fever and chills. you may get cramps and then of course very urgent loose stools in various amounts. sometimes there is vomiting or bloody diarrhea. with norovirus onset can be sudden and vomiting is a much more prominent feature. for bacterial and viral travelers' diarrhea the incubation period is typically six to 48 hours after infection. for protozoan travelers' diarrhea there is usually more of a gradual onset with a few loose stools per day and increased gas and nausea. the incubation period can be one to two weeks.
aside from the obvious how do you know you're coming down with travelers' diarrhea?