Caliciviruses (norovirus and sapovirus) cause outbreaks of viral gastroenteritis in closed and semi-closed populations such as long term care facilities and schools. Caliciviruses can also cause outbreaks of foodborne illness. Viral gastroenteritis has a disinctive clinical syndrome of diarrhea and vomiting, comes on rapidly, and leaves victims miserably ill for a couple of days. Caliciviruses are very, very contagious.  Because calicivirus outbreaks occur mainly in the colder months, an early name for such outbreaks was “winter vomiting disease.”