A norovirus outbreak in 11 northern Nevada schools has sickened hundreds of young children and some teachers, officials said.

The Washoe County Health District said it believes the norovirus outbreak first started on Sept. 16 at a Reno elementary school, where 150 students and 11 staff members have reported symptoms, including nausea, vomiting, diarrhea and abdominal cramping.

As of Friday, the Washoe County School District reported that the outbreak had spread to 9 other elementary schools, a high school and some associated daycare centers. It has been centered in Reno, with one Sparks elementary school.

No one has died or been hospitalized by the latest outbreaks.

Most of the nearly 400 people affected have been elementary school children. The high school teachers who were sickened also traced their illnesses to the affected elementary school kids, whom they were related to.

"Elementary school kids, younger kids probably aren't the best when it comes to hygiene," said Phil Ulibarri, a county health department spokesman.

The bacteria and viruses that cause the illness can be airborne, entering the body through the mouth.

County health officials are working to document and contain the outbreak but warn sick students and adults to stay home for at least 72 hours until the symptoms subside.

The school district has also been advised to thoroughly clean schools, which Ulibarri said means sanitizing a 25-foot radius where there is vomiting or diarrhea, including going as high as six feet up along walls.

Health officials also urge parents to properly clean surfaces when there are sick children at home.

"You know kids. They're touching each other, toys, common toys, common surfaces — things like telephones and keyboards, snack tables," Ulibarri said.

The county dealt with another outbreak in 2012 when more than 1,400 children were sickened by the same gastrointestinal illness. The outbreak died down when schools closed for Christmas break and staff was able to perform thorough cleanings.