Diana Samuels reports that an outbreak of norovirus has sickened more than two-dozen people at The Sequoias in Portola Valley, an official at the retirement community said Tuesday. Officials have closed the retirement community’s dining room and canceled social activities, said Rick Isaacs, The Sequoias’ skilled nursing administrator. Family members and others are “encouraged not to visit, for the time being,” he said, as staff works to keep the illness from spreading.

Norovirus causes diarrhea, vomiting and stomach pain, and is spread from person to person through contaminated food or water and by touching contaminated services, according to the Centers for Disease Control and Prevention’s website. It is recognized as the leading cause of foodborne-disease outbreaks in the United States, the CDC site says. No more than a dozen people at The Sequoias have been sick at any one time since officials at the retirement community learned of the outbreak mid-last week, Isaacs said.