INDEPENDENCE, Iowa (AP) -- Health officials suspect a norovirus outbreak is behind dozens of students getting sick in the Independence school district in northeast Iowa.

The Waterloo-Cedar Falls Courier says Superintendent Jean Peterson says 30 students were sent home last Thursday and another 20 on Friday. There was no school on Monday because of the Presidents' Day holiday.

Amy Marlow of the Buchanan County Health Department says all the symptoms point to the norovirus, a quick-spreading bug that includes diarrhea, vomiting and stomach cramps.

State medical director Dr. Patricia Quinlisk says norovirus is highly infectious and people need to stay home when they are ill.