A Santa Monica middle school was ordered closed Friday after nearly 200 students were potentially exposed to norovirus during a recent trip to Yosemite, officials said.

The Santa Monica-Malibu Unified School District said that students from John Adams Middle School were on a five-day trip to Yosemite last week when some participants showed signs of gastrointestinal illness.

Classes were canceled Friday, and no students or staff will be allowed on the campus, Principal Steve Richardson said in a statement. All activities on campus are canceled from Friday through Sunday, with the exception of field sports.

A planned trip for eighth-graders to AstroCamp, a science camp in the San Jacinto Mountains near Idyllwild, has also been canceled, Richardson said. School officials are planning to provide refunds for the trip, which was supposed to take place this weekend, Richardson said.


Several teachers and parents were potentially exposed to the virus as well, according to a letter sent to parents and staff and published on the school district’s website. It’s unclear how many people were infected in total.

School officials notified parents of students at John Adams Middle School on Sunday, and officials at the Los Angeles County Department of Public Health have helped trace the outbreak to the Yosemite trip.

About 190 seventh-graders were on the trip, along with the teachers and parents. The group returned Friday from Yosemite but did not step onto campus until classes resumed Monday morning, district officials said.

Officials believe the same illness spread to other students at the school who were not on the Yosemite trip, as well as to siblings who attend other schools within the district.


“The challenge with this highly contagious illness is that a child or adult may still feel well when they are contagious, making containment difficult,” according to the district’s letter.

School officials said they were working with public health officials to prevent the spread of the illness. Classrooms and other facilities were being cleaned with special products recommended by public health officials.

Public health professionals “anticipate that due to its highly contagious nature and the escalation in affected cases this week, this infections cycle could extend weeks at [John Adams Middle School] and spread to other campuses unless immediate measures are taken,” Richardson said.

On the trip, students rode by bus to Yosemite and slept in tents in Curry Village and dormitories in Crane Flat. The trip was billed as a way to stay “far away from any shiny screens and electronics,” according to the school’s website.


Norovirus is a contagious organism that can be spread through contaminated food or water and human interaction, according to the Centers for Disease Control and Prevention.

Between 19 million and 21 million illnesses are caused by norovirus each year, and it is considered the most common cause of food-borne disease outbreaks in the U.S.

Those infected typically experience inflammation of the stomach and intestines as well as nausea, vomiting, diarrhea and stomach pain.

matt.hamilton@latimes.com


Twitter: @MattHjourno

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UPDATES:

7:55 a.m.: This article was updated with information about the school closing.


This article was originally published at 9:45 p.m. Thursday.