My Brother, Who Is 40 Years Old, Had Vomiting For

My brother, who is 40 years old, had vomiting for 26 hours straight. He had extreme vomiting for the first 12 hours-vomiting every 30 mins along with stomach cramps. He is not one to complain, but when this happens it is very intense. So far this has happened to him three times this year. He has a wife and two young kids who don't experience these symptoms, so it's hard to believe it is the flu. What is your opinion on the possible causes?