By Betty Yu

SAN JOSE (CBS SF) — Ten schools in the San Jose Unified School District have reported being impacted by the norovirus, school officials said Tuesday.

The elementary schools affected are: Hacienda, Horace Mann, Olinder, Washington, Grant, Ann Darling, Carson, Terrell and Willow Glen.

The only middle school affected as of Tuesday, was John Muir Middle School, according to school officials.

Cleaning crews are now scrubbing down nearly every inch of classrooms and playgrounds at Hacienda Environmental Science Magnet School, one of 10 schools in San Jose reporting an outbreak of the stomach flu, believed to be caused by norovirus.

Though the virus is common, this is an unusually high number of cases for Santa Clara County.

Dr. George Han, assistant health officer for Santa Clara County said norovirus, “is also known as winter vomiting disease.¬†People call it that because that tends to be the season that it comes around, when it’s colder, and so for whatever reason there’s more of it now.”

And it’s easily spread, especially among young children.

Han said,¬†“After going to the bathroom, if the person doesn’t wash their hands with soap and water vigorously, then they might still have some virus left in their hands and then they touch someone else, touch a surface, somebody else touches it, and then they touch their mouth — that’s how you get infected.”

Some 200 students have come down with symptoms including vomiting and nausea since early May. It’s forced schools to cancel events.

San Jose Unified School District Public Information Officer Peter Allen said, “It’s a challenge. I know at least one of our schools the principal was proactive about postponing or canceling a lot of non-instructional events. So like art shows, performances, things that we know parents and students get really excited for, and it really does break our hearts to have to put those things off or cancel them.”

Norovirus is considered a mild illness but the district is urging parents to keep their kids at home for 48 hours after they get better. Even after symptoms disappear, children can spread the virus for up two days afterward.