Covid-19: Outbreak in NSW hospital cancer ward

New South Wales authorities say several patients and staff members at a southern Sydney hospital's oncology ward have tested positive to Covid-19.

Three patients and two staff members at St George Hospital in Kogarah contracted the virus. The hospital is treating all patients in the ward as close contacts.

Dr Anthony Holley, the President of the Australian and New Zealand Intensive Care Society, said it was very concerning but not unexpected.

"These are the most at-risk patients in many ways, particularly immunocompromised patients that might be found in an oncology ward.

"So, despite the best care taken by health professionals to avoid cross-infection within the hospital setting it still remains a possibility," Dr Holley said.

NSW prison authorities said four inmates at Silverwater jail's remand centre have also been confirmed as having coronavirus.

They are all being housed in isolation in line with Covid-19 protocols.

On Monday the state recorded its worst day so far of the outbreak with 478 new cases and eight deaths. ​

Authorities say they are concerned by the number of Covid-19 cases emerging in the city of Dubbo in the state's central west.

Of the 99 active cases in the Western NSW local health district, more than 90 are in Dubbo, and 40 percent are in children aged 10-19.

Several schools have been shut after students and staff tested positive.

Chief health officer Kerry Chant said she was particularly concerned about the impact the virus was having on Aboriginal communities in the area.

Australian Defence Force personnel will arrive in the western city today to help local health officials, whose resources are stretched.

Communities in Bourke, Parkes, and Lennox Head were told to be vigilant after traces of the virus was found in sewage.