Schools in the Nelson-Tasman region are being warned to take preventative action against the highly infectious norovirus which has affected one of the region's biggest colleges.
Nearly a third of the teaching staff at Waimea College in Richmond are off sick.
Medical officer of health Jill Sherwood said on Wednesday a letter has been sent out to all schools in the area to remind them of the importance of cleaning toilet facilities thoroughly.
They have also been told to make sure they have disposable paper towels and soap dispensers in order to reduce the risk of infection.
Dr Sherwood is advising people to stay away from work or school for 48 hours after their last episode of diarrhoea or vomiting, to avoid passing the bug on to others.