Stomach flu, or gastroenteritis, can spread very quickly in schools, resulting in high levels of absenteeism. The virus can live for a long time on surfaces so effective cleaning and disinfecting is important. As with most contagious illnesses, hand washing is also a very important preventive measure.
People can still spread a gastrointestinal virus for several days after they recover. In an outbreak, Public Health will often recommend ill children and teachers stay home for two days after their symptoms stop.