A school district in western Arkansas will remain closed for the week after more than 300 students reported being sick with the flu, school officials said Tuesday.

Horatio Public Schools said in a notice to parents that the district has canceled classes until Feb. 4, “to prevent further illness and loss of instructional time.” Students at the Sevier County district were let out of class around noon on Tuesday, officials said.

For Superintendent Lee Smith, it’s the first time he has had to cancel school because of an illness outbreak, which he said saw more than 20 percent of students and several teachers absent from class on Monday.

“Today it was worse,” he said.

Roughly a third of students at the 950-population district missed school Tuesday and either had confirmed cases of the flu or had flu-like symptoms, Smith said.

Smith faults low numbers of getting flu shots, saying that nearly all of the 170 or so students who had a flu shot didn’t report getting sick or only had mild flu symptoms.

“This year it just didn’t seem to be a priority and now we’re paying the consequences,” Smith said. Increasing the number of students who participate in the school flu shot program will be a priority next year, he said.

The flu can be deadly in younger children who aren't vaccinated, said Jennifer Dillaha, the medical director for immunization at the Arkansas Department of Health. That's because they likely haven't had the flu, so their immune system isn't as strong at fending off the virus, she said.

The state Department of Health on Tuesday raised the spread of this year’s influenza outbreak across the state, denoting it as “widespread,” or when the flu is prevalent in a majority of the state.

The weekly report said this year’s dominant strain, H1N1, was confirmed at far higher rates in children at teenagers younger than 18 than other ages.

Twenty children and teens were admitted to Arkansas hospitals because of the flu since Sept. 30. The agency reported 17 deaths across all ages, including one pediatric death.

Though this year's rates appear lower than last year's nasty flu season, Dillaha said the worst of this year's season has yet to come.

“The flu season has not peaked yet,” she said. “We want people to go ahead and get the vaccine so they have time to develop an immunity.”

School officials at Horatio meanwhile are planning to disinfect the school and allow the flu virus - which has a four to five day incubation period - to run its course.

“It will hopefully give it a chance to die out,” Smith said.