More than 50 staff and residents have tested positive since the outbreak was detected, which began when an infected employee worked for several days before being diagnosed.
Anglicare, which runs the home, said it is “deeply saddened” by the latest deaths.
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“We extend our deepest sympathies to these families for the losses they are experiencing,” it said in a statement.
“On the best advice available, we know that it will be some weeks before the home is clear of the virus.
“For those residents with a positive COVID-19 diagnosis, NSW Health has provided the support and guidance of Nepean Blue Mountains Local Area Health Network and an Infectious Diseases Specialist to ensure residents receive the best medical care possible.”
The Federal Government was forced to intervene last week when it emerged that Newmarch House was significantly understaffed.
Loved ones of residents voiced their concerns about the quality of care being offered.
“This is a tragic time not only for the families who have lost their loved ones but for other residents and families,” Anglicare said.
“It is also taking a deep toll on our staff who cared for and knew these residents and families so well.”
The shocking news today comes as multiple states confirmed their plans earlier on Tuesday to begin relaxing some social distancing restrictions.
Although, not all jurisdictions are on board.
Australia has now recorded 6728 confirmed cases of COVID-19, including 3009 in New South Wales, 1351 in Victoria, 1033 in Queensland, 438 in South Australia, 550 in Western Australia, 214 in Tasmania, 106 in the Australian Capital Territory and 28 in the Northern Territory.
A total of 89 deaths have been recorded nationally.
The details of the four deaths today are yet to be confirmed but it is understood a 93-year-old man is among the four who have died.