A Waikato prison is grappling with a mass illness that started on Christmas Eve.
One Spring Hill Corrections Facility prisoner has been confirmed to have campylobacter, while a total of 47 prisoners have informed staff that they are unwell.
Acting Prison Director Megan Tuhoro said they were working closely with the Waikato District Health Board's Public Health Service to establish what caused the prisoners to become unwell over the past week.
The first reported case of a prisoner becoming sick was on Christmas Eve.
There are currently 879 prisoners accommodated on site.
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"As a result of concern for their pre-existing health conditions, four prisoners were taken to hospital for assessment as a precaution, however none were admitted and all four are being cared for at the prison," she said.
"Registered nurses are monitoring prisoners' wellbeing and all staff on site have been briefed on the care plan for unwell prisoners."
That includes close observation, hydration, electrolyte replacement, rest and paracetamol for pain relief.
"There have been no complaints received relating to toilet paper being unavailable, with plenty of stock on site," Tuhoro said.
"There have also been no complaints in relation to laundry, with fresh stocks available as required."
The source of the infection is currently unknown.
"All prison meals are prepared in industrial kitchens under the direct supervision of Instructors working within the National Food Control Plan.
"There are clear and well-established quality and hygiene practices and policies to ensure that all food is prepared safely and to a high standard."
Public Health advice is that people with campylobacter may become unwell two to five days after contracting the infection, she said.
Potential infection sources can include contaminated food or water, direct handling of animals, or cross contamination via substandard hygiene practices (for example, contaminated chopping boards or those preparing food not washing their hands thoroughly before preparing food).