Norovirus sickened more than 300 students at an Arkansas middle school last week, causing the school to shut its doors Friday. At least a third of the 900 children who attend Hellstern Middle School in Springdale and several staff either stayed home or fell ill at school Thursday, complaining of gastrointestinal symptoms, reported NWA. At the time, the cause of their illnesses remained unknown. Then on Monday, health officials announced that Norovirus was likely the responsible pathogen. All stool samples taken from sick children tested positive for the virus, said Springdale district spokesperson Rick Schaeffer, according to NWA. Norovirus infection is characterized by an inflammation of the stomach that causes stomach cramps, diarrhea, nausea and vomiting. The Centers for Disease Control and Prevention estimate that over 20 million people experience acute gastroenteritis from noroviruses each year. The virus is spread easily from person to person via the fecal-oral route, and is especially common in enclosed places such as daycares, cruise ships and long-term care facilities. Parents of children affected by this outbreak say their kids are recovering. The school is scheduled to reopen Tuesday. “Classes will resume at all schools, including Hellstern, Tuesday morning,” Schaeffer told NWA Monday. “Hellstern has been completely disinfected and every bus utilized by the Springdale district was sterilized Thursday evening. We are anticipating school as normal. Obviously we will be monitoring the attendance at Hellstern.”