Knowledge of a serious hospital fungal outbreak that claimed the lives of two transplant patients was kept from the relevant minister for more than a month after health authorities discovered it.

NSW Health Minister Ryan Park's office was alerted on Christmas Eve to possible fungal-related deaths and illnesses in the Royal Prince Alfred transplant unit, related to the hospital's $940 million redevelopment.

Hospital management had been investigating the matter since early December.

But Mr Park admitted on Monday he was unaware of the two deaths and four illnesses until well after his return from holidays on January 5.

"(The rough date would have been) the first part of February, I don't have a date where I've written something down," he told a budget estimates hearing.

The ward was reopened on February 9 on advice from an expert panel.

The troubles inside the 143-year-old tertiary hospital, often at the cutting edge of medicine, were followed on Monday by the revelation of substantial maintenance and pest issues across the state's 4400 health buildings.

The cause of the infection in Royal Prince Alfred was Aspergillus, a common mould found in soil, dust and damp environments.

Six patients in its transplant unit were affected by the fungal cluster in late 2025, hospital management confirmed on Thursday.

The cause was construction works linked to a $940 million redevelopment.

People are unlikely to become unwell from Aspergillus but it can be particularly damaging for certain individuals with weakened immune systems, the health department said.

Opposition health spokeswoman Sarah Mitchell said the communication breakdown in the department was unacceptable.

"How can you not know when there's been a major outbreak, and hundreds of people needed to be informed about it?" Mrs Mitchell asked Mr Park on Monday.

Ahead of his appearance at budget estimates, Mr Park detailed the results of a snap maintenance review on Monday.

Outbreaks of cockroaches, possums, birds and insects at major hospitals were revealed.

There are 38 non-routine maintenance issues still unresolved from the last year, Mr Park said.

These include ongoing pigeon infestations at Tamworth and Royal Prince Alfred hospitals, and five hospitals needing roof repairs.

"I would like every building to be perfect and new," Mr Park said.

"The challenge is that with a portfolio this size, you're always going to need to be on top of maintenance."

As well as current maintenance problems, the snap probe identified major infestations in the past decade that were never reported.

Flies, cockroaches, birds and possums were found in major Sydney and Central Coast hospitals, including Westmead and Royal North Shore, between 2012 and 2019 without being reported in the press.

Meanwhile, doctors have welcomed the continuation of private healthcare at another embattled Sydney hospital until June next year.

Northern Beaches Hospital was bought by the NSW government from private operator Healthscope after the death of toddler Joe Massa in 2024.

His death sparked a campaign prompting the passing of a law banning future private-public hospital partnerships.

But the decision to maintain the provision of private services on the eight-year-old site is crucial to protecting the clinical services and workforce in the area, the NSW branch of the Australian Medical Association says.

"Private services at Northern Beaches Hospital are not an optional extra," branch president and local obstetrician Kathryn Austin said.