A Southern California school closed Friday to try to halt further spread of suspected norovirus contagion that appeared among a large group of students who attended a science camp at Yosemite National Park last week.
The Santa Monica-Malibu Unified School District said 190 seventh-grade students from John Adams Middle School, along with some parents and teachers, were potentially exposed to the gastrointestinal illness during the five-day Yosemite trip.
The district said it is working with the Los Angeles County Department of Public Health to contain the illness, which appeared to have spread to some John Adams students who didn't go on the trip and through siblings to other Santa Monica schools.
The health agency "currently believes that this originated in Yosemite, potentially exposing students from dozens of school districts," the district's statement said.
The students on the trip returned to Santa Monica on Jan. 27 and did not return to the campus until last Monday.
The highly contagious norovirus can be transmitted from an infected person, contaminated food and water or by touching a contaminated surface, according to the federal Centers for Disease Control.
Infections cause inflammations of the stomach and intestines. Symptoms include nausea, vomiting, diarrhea and fever.
All ages are susceptible to the virus, and the symptoms can become serious for very young patients and older people, the CDC said. People can get the illness repeatedly because there are many types of noroviruses.
The most common period for norovirus outbreaks in the United States is from November to April.
The Santa Monica district urged parents to keep any child with symptoms at home and to alert their school. Students should also be kept at home for three days after the end of any symptoms because they remain contagious, the district said.
The John Adams Middle School campus will remain closed through Sunday for cleaning. Any other sites where a case occurs will also be cleaned, the district said.