The hospital in the South Otago town of Balclutha has stopped taking patients as staff battle to contain an outbreak of gastroenteritis.
Clutha Health First has closed its inpatient ward to patients transferring from other hospitals but is continuing to accept acute admissions from GPs and emergency services on Monday.
Chief executive Ray Anton says patients and staff have been affected by the virus, which causes severe vomiting and diarrhoea.
Mr Anton says access to the infected ward has been restricted to essential visits from immediate family only, and anyone presenting symptoms of a stomach virus should stay away for at least 72 hours.
The maternity ward and other departments are not affected by the outbreak.