Victoria's nurses' union claims the state's neonatal intensive care system is at breaking point after a mystery illness hit more than a dozen babies in a hospital nursery.
Fifteen newborns being cared for in The Royal Women's Hospital's intensive and special care nursery were quarantined when the illness emerged nine days ago.
Two had to have surgery for an inflammatory bowel condition.
A Royal Women's Hospital spokeswoman said there was no danger to new arrivals.
Australian Nursing Federation state secretary Lisa Fitzpatrick said she was concerned about the stress on neonatal care units across the state.
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"There is continuing pressure put on those units and we know that there has been an issue this week with 20 babies still being barrier nursed," Ms Fitzpatrick said.
More than 1900 specimens had been taken to determine the cause of the outbreak, she said.
"We have pregnant staff in that unit and nurses working up to 14-hour shifts to take care of those babies," she said.
The state opposition blamed funding cuts for the stress in neonatal units, but the state government said it had been increasing the number of neonatal intensive care beds.
