JEWELL — Jewell School has closed until Friday because of a flu outbreak affecting more than a third of the school district.

Alice Hunsaker, the school superintendent in Jewell, said in a release that the decision was made Monday in partnership with the Clatsop County Public Health Department after more than 35 percent of students in the school district came down ill with the flu, along with a significant percentage of faculty.

“During our closure the school custodial and maintenance staff will be conducting a thorough cleaning and disinfecting, again, following state guidelines for this comprehensive antibacterial and virus process,” Hunsaker wrote.

Michael McNickle, the county’s public health director, said it recommended the school close for three days.

“Influenza A has a longer incubation period,” McNickle said. “We kept it closed three days to make sure those affected don’t infect others.”

The county sent a nurse to Jewell to administer up to 55 free doses of flu vaccine, some of it borrowed from Coastal Family Health Center.

“The supply has become kind of tight because of all the flu rampaging throughout the U.S.,” McNickle said.

Knappa School District last year closed Hilda Lahti Elementary School for two days because of a flu outbreak affecting more than 40 percent of students. The outbreak was the only other instance of a flu-related school closure in the past several years, McNickle said.

The percentage of admissions to hospital emergency departments for flu-related illnesses has been steadily increasing throughout February, according to statistics from the Oregon Health Authority. The percentage of admissions related to the flu peaked in late January to early February the past two seasons.

As of Wednesday, 41 children had died of the flu this season, according to the federal Centers for Disease Control and Prevention. The CDC recently reported that this year’s vaccine is proving 47 percent effective at preventing the most prevalent strains of the flu.