More than a hundred college students in Illinois have announced that they were sick earlier this week because of an isolated flu outbreak.
At least 158 of the 884 students at South Middle School in Arlington Heights were ill Tuesday, while 185 of them were called on Wednesday because of possible influenza cases, CBS reported Chicago.
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At least 31 of the students were confirmed to have a certain strain of influenza called A flu, according to the television channel, quoting a spokesman for South Middle School.
The massive absence prompted school officials to send a letter to parents.
"Our surveillance team treats certain areas of the building more frequently to help prevent the spread of germs," the letter says, in part, according to CBS Chicago. "Many of our teachers have asked their students to use school supply wipes to treat personal items and the surfaces around them in the classroom / lockers."
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The school reportedly contacted the Cook County Health Department to find out how to control the spread of the virus.
Neither a spokesman for the health department nor South Middle School immediately responded to Fox News' request Friday to comment on the outbreak.