Two schools in Anchorage -- Dimond and Service high schools -- were particularly hard hit. Friday alone about 80 students were sent home sick in the district. Another 140 called in sick at one school, far higher than the average, the Anchorage Daily News reported.
The illness causes unexpected nausea, vomiting and diarrhea.
Most of the students felt better between 12 and 48 hours after the onset of symptoms, the Daily News said.
State epidemiologists were investigating the outbreak. They were interviewing students, and taking stool and vomit samples from those infected to determine the precise origin of the bug.