A Western Sydney aged-care home is in lockdown after a staff member who tested positive to coronavirus worked six shifts while showing symptoms of the deadly bug.

Key points: One resident in the aged-care home has subsequently tested positive for COVID-19

One resident in the aged-care home has subsequently tested positive for COVID-19 Another resident is also developing symptoms and has been tested

Another resident is also developing symptoms and has been tested The NSW Health Minister said the worker put vulnerable people at risk

The female staff member worked shifts at the Anglicare Newmarch House in Caddens, and Greystanes Disability Services in Leura while infected.

On Saturday, the woman tested positive to COVID-19, leaving health authorities scrambling to identify her close contacts at the Caddens facility, where one resident has subsequently returned a positive swab for the virus.

NSW Health says it is waiting for test results from a second ill resident at the aged-care home.

Matthew Fowler's father Lionel is a resident at Newmarch House, near Penrith, and is now in self-isolation.

Mr Fowler said the fact the sick staff member continued working despite showing coronavirus symptoms was "not good enough".

"[My father] doesn't know where else he would go other than a hospital if he was symptomatic, but for me, that would be too late anyway," he said.

He said there was a still a "big question mark" over how many other elderly residents of the facilities could have been infected over the six days.

"I do feel anxiety in terms of the fact that we don't know how many other staff may have been obviously exposed," he said.

The chief executive of Greystanes Disability Services, Robert Tinsey, said one house in Penrith had been placed into quarantine after the worker tested positive.

"Everyone is in good health and spirits so far and we're hoping that will remain," he said.

Residents at Newmarch House have been placed into isolation. ( ABC News )

In a statement, Anglicare said residents at Newmarch House were in isolation and staff were now wearing personal protective equipment (PPE).

NSW Health Minister Brad Hazzard said the worker had put vulnerable people at risk.

"We have talked about this numerous times but now it appears that some staff are still going to work, even when they have symptoms," he said.

"Please don't go to work if you're feeling sick. Just don't go."