Hospital general manager Simon Donlevy said yesterday five patients and nine staff had so far come down with gastroenteritis, and the situation was being reviewed daily.
The outbreak of the intestinal infection was detected on Tuesday , and HNZ announced on Thursday the medical and surgical wards had closed to visitors to protect patients and staff.
Compassionate grounds for visiting the wards, where 77 patients were being cared for yesterday, could be discussed with the charge nurse manager.
Mr Donlevy said limiting the number of people on the ward would help reduce the spread of the illness.
"Gastroenteritis is highly infectious, meaning it can be passed to others easily through hand-to-mouth contact after handling a contaminated surface or object and through the air by inhaling airborne infectious particles," he said.
"Key symptoms include nausea, vomiting, diarrhoea, headache, chills, muscle aches and fever."
Southland Hospital had not faced ward closures caused by gastroenteritis for at least three years, he said, describing the situation as "very rare".
Healthcare workers were following infection prevention and control measures including strict hand hygiene, case isolation, regular cleaning, and disinfection.
"Gastroenteritis can be easily transmitted, especially where there is an infection in areas and especially bathrooms that are shared by multiple people," he said.
People with symptoms were advised to stay home until 48 hours after the last episode of vomiting or diarrhoea.
"To reduce your risk of catching or spreading gastroenteritis, wash your hands well after using the bathroom or changing nappies, and before eating or preparing food."
Most cases got better without any specific treatment, although staying hydrated was important, he said.
People with symptoms who needed medical help were advised to contact their GP or pharmacist, or come to the emergency department or call 111 if it was urgent.
There was no evidence the situation was related to the Queenstown Cryptosporidium outbreak, he said.
"We will provide an update once these wards are open again to visitors.
"We thank our community for helping us keep our patients safe."
