It has now been revealed three nurses working for Waikato District Health Board have tested positive for coronavirus.
It was orginally announced that two staff members on a ward for older people at Waikato Hospital had contracted the disease.
Eighty staff have been stood down indefinitely, while the Waikato health board traces their movements.
Some could return next week, but others may have to be off work for 14 days.
Health board chief executive Kevin Snee said staff and inpatients on the ward had been contacted, and none had any symptoms.
"It's obviously a concern if you have Covid-19 in proximity to other people with comorbidities, so it's critically important that we do track down and test people who've been in contact with the nurses, but to date we haven't identified any patients with Covid-19," Dr Snee said.
Dr Snee said staff from other wards had been redeployed to make up the shortfall.
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