Seven people from the Hilltops region have been diagnosed with the virus since Thursday, with five of them being transferred to and cared for in Wagga Base Hospital.

The neighbouring local government area of Cowra will head into lockdown on Monday afternoon, chief health officer Dr Kerry Chant said, after a nine-year-old contracted COVID-19.

"Anyone who was in Cowra from September 13, regardless of where they are, must adhere to the stay-at-home requirements," Dr Chant said.

"There was a nine-year-old boy who attended school in Cowra and there were a number of associated community exposures. The source at the moment is under investigation."

The three MLHD cases announced late on Sunday - a woman in her 70s and a male household contact in his 40s, and another man in his 50s - are formally counted in the figures revealed by NSW Health and the premier in the Monday statewide update.

The daily case number dipped back to three figures, with 935 new cases detected across the state in the 24 hours to 8pm Sunday, premier Gladys Berejiklian said, and four people died.

In other news

Two men in their 60s from south western Sydney died in Liverpool Hospital, a woman in her 80s from the Wollongong area died in Wollongong Hospital and a western Sydney man in his 80s succumbed to the virus in Nepean Hospital. His death is the second linked to the outbreak at Penrith's Uniting Edinglassie Lodge aged care facility.

There are 1,207 COVID-19 cases admitted to hospital, with 236 people in intensive care, 123 of whom require ventilation.

"I should note that even if case numbers go down, we should expect unfortunately that the number of people in intensive care and the number of people who lose their lives to go up because as we've said consistently because we have had a number of cases in the last few weeks, people ordinarily get very sick in the second week of the illness and sometimes stay very sick for a long time," Ms Berejiklian said.

"That is why we need to continue to brace ourselves for October being the worst month for the number of people who pass away and the number of people who need intensive care. We should never lose sight of that, no matter what else is happening."

The majority of new cases are concentrated in Sydney local health districts [LHDs], but almost 150 new diagnoses were made in regional areas.

The Nepean Blue Mountains LHD recorded 49 new cases, another 45 were found in Illawarra Shoalhaven, the Hunter New England has 24 fresh cases, the Central Coast is home to 19 new COVID-19 patients, Western NSW has 10 - including the Cowra case - and Murrumbidgee has three, all of which were reported on Sunday.

The interstate, trans-Tasman situation

Fragments of the virus have been detected in sewage surveillance at Albury, Young, Griffith, Balranald and Cowra in recent days. Concerns are also held for the far western NSW community of Dareton, near Mildura on the Victorian border, where virus fragments have also been found in the treatment plant.

There are no known or recent cases at Griffith and Balranald, and a case emerged at Cowra late on Sunday.

Western NSW LHD confirmed the positive test in Cowra was now isolating outside the township with household contacts.

Coles Cowra has been listed as a venue of concern for the Friday, September 17 between 11.20am and 11.40am.

Griffith's mayor, John Dal Broi, said he was disappointed, but not surprised that the detection had been made after it was announced by NSW Health's Dr Jeremy McAnulty on Saturday.

He said there is often an influx of people in Griffith between farming activities and infrastructure and development projects.

The mayor also said he doesn't know what the source of the positive fragments might be.

"You'd like to think it's someone just passing through, but we just don't know," Cr Dal Broi said.

"We can't shy away from it, we've just got to accept it and do what we can."

Extra testing is available on Monday in Young, Harden, Boorowa, Cootamundra, Temora and Albury, the MLHD advises.

People can get tested at the following locations, and appointments are not necessary unless specified:

For additional testing locations go to www.mlhd.nsw.gov.au, or for help accessing a test call the Murrumbidgee COVID-19 Hotline 1800 831 099.

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