The illness that closed a Westport primary school this week has been identified as influenza, the West Coast District Health Board says.
Westport North School was forced to shut its doors on Tuesday after 66 students - one third of its roll - fell ill with headaches, nausea, fevers and vomitting.
Samples taken from the school have returned positive for influenza.
DHB Medical Officer of Health Ramon Pink said those who had been sick should stay home from school or work for at least five days after first experiencing symptoms.
He also urged people to call a GP for medical advice rather than visiting in person.
