Norovirus is a common, easily spread virus that causes various forms of gastric distress.
The students apparently became ill on Tuesday and Wednesday night after eating at the dormitory on the Palo Alto campus, a school official said. The official said the symptoms appeared to be in a pattern consistent with norovirus.
The dormitory is now undergoing a complete sanitizing including all bathrooms and common areas.
School officials are informing the 433 residents of the dorm to "be vigilant about hygiene" because the norovirus can spread for more than three days after the initial infection.It is unclear how the outbreak started.