Deputy Premier John Barilaro says he expects COVID-19 cases in western NSW Indigenous communities to spike as ADF troops arrive to help with vaccinations.

The week-long lockdown imposed on NSW regions last weekend will be reviewed by crisis cabinet as the COVID-19 outbreak gripping the state entrenches itself in rural communities.

Deputy Premier John Barilaro said it was "premature to have that conversation" on the day NSW notched up a record 633 new infections and he predicted a spoke in Indigenous communities in the west.

Seventeen of the 23 new cases recorded in western NSW were in Dubbo, with the remainder in Mudgee, Narromine and Gilgandra.

After the first case was recorded in outback Broken Hill on Monday, there are now four others in the state's far west, with three in Wilcannia and one in Bourke.

The government imposed a snap seven-day lockdown for rural NSW last weekend, plunging the entire state into stay-at-home mode in order to quell the spread of the virus.

Mr Barilaro conceded the numbers had been going the wrong way ever since.

"So it's a 50-50 call, one that the crisis committee will make (and) one that we'll absolutely be upfront with the community sooner rather than later," he said.

Australian Defence Force troops arrived in Dubbo, as well as Newcastle in the Hunter, on Wednesday as the crisis escalated and authorities pleaded for people to get vaccinated, stay home and comply with strict state-wide lockdown measures.

"It is clear that this issue in central and western NSW is where our focus and our priority is and the message for everybody is to follow the stay-at-home orders, cut down mobility," Mr Barilaro said.

The ADF will work with local health authorities to help vaccinate and test people, conduct welfare doorknocks and compliance checks in vulnerable Indigenous communities where vaccination rates are low and risks are high.

"It is already in those communities and this is what is concerning us," Mr Barilaro told the Nine Network.

"The mobility in those communities, the shared homes, the houses, we know that with Delta most of the infection is happening in somebody's home or visiting somebody.

"I expect it to spike and I expect it to continue to be a problem and that is why we locked down all of regional and rural NSW because it was the only way we could contain this."

Fragments of the virus have been found in sewage treatment plants at Yamba on the north coast as well as Bathurst, west of the Blue Mountains, and Orange in the Central Tablelands.