At least 65 conferencees came down with norovirus during a medical conference in Maryland, reports AP news. Norovirus, sometimes called the stomach flu, is usually spread when an ill food preparer accidentally contaminates the food. Just 9 viral particles is all it takes to infect a healthy person. Typical symptoms are diarrhea and vomiting. Most people recover just fine, though people with weakened immune systems, very young and very old people can suffer from complications.