Greymouth hospital has been hit by an outbreak of diarrhoea and vomiting.
Around half a dozen patients and staff from Grey Base Hospital's Morice Ward have come down with gastroenteritis in the past few days.
Morice Ward is a general medical ward, which can hold up to 17 patients.
Doctor Vicki Robertson said visitors had been asked to stay away from the ward, and the restriction is likely to stay in place until Sunday.
"So we want to limit spread, and in fact closing the ward has resulted in no new cases in gastroentiritis occurring since seven o'clock yesterday morning when the ward was closed."
Ms Robertson said anyone who is feeling unwell should stay away from the entire hospital.