SANTA MONICA—A contagious gastrointestinal illness spread amongst a group of students from John Adams Middle School (JAMS) in Santa Monica after a five-day science field trip to Yosemite, according to reports disclosed on Thursday, February 2.

Around 190 seventh-grade students, as well as teachers and parents, from JAMS were on the trip; they returned on January 27, but did not return to the school until Monday, January 30. In addition to the travelers, the illness appeared to have spread amongst other JAMS students, and individuals from other Santa Monica schools through siblings. The total number of people who contracted the virus is unknown.

The Los Angeles County Department of Health deemed the illness to be norovirus, a contagious organism that causes inflammation of the stomach and intestines which can lead to symptoms such as nausea, diarrhea, vomiting, and fever. It can be spread through direct contact with an infected person, as well as contaminated food or drink. Authorities from the Department of Health asserted that the illness could potentially be exposed to students from “dozens of school districts.”

The Center for Disease Control (CDC) said that people of all ages can contract the virus, and it can be dangerous for the elderly and very young children. In addition, “people can get the illness repeatedly because there are many types of noroviruses,” CDC staff shared with the Associated Press.

Officials from the Santa Monica-Malibu Unified School District sent out a letter to families, sharing that “The challenge with this highly contagious illness is that a child or adult may still feel well when they are contagious, making containment difficult.”

The district announced that the school, along with all campus activities, would be closed on Friday, February 3 and the weekend (with the exception of field sports) to prevent the illness from spreading further. JAMS Principal Steve Richardson also indicated that an eighth grade trip to AstroCamp, located in the San Jacinto Mountains was also canceled. Members of the school board plan to provide refunds to students and their families.

During the closure, janitorial staff will be cleaning the campus (with anti-bacterial disinfectants), as well as “any other classrooms and facilities where we learn of a case,” district officials noted.