The widespread nature of these cases comes as NSW Premier Gladys Berejiklian and Deputy Premier John Barilaro both suggested the Hunter outbreak had stabilised in the past few days, with another 16 cases announced on Monday.

However, University of NSW Professor Mary-Louise McLaws, a high-profile epidemiologist, said: "It's too early to be certain that there is no further threat from Delta in the general Hunter New England region."

Nonetheless, some regions appear better placed to contain the virus than Sydney.

"We know communities that are highly interconnected experience rapid and wider spread with Delta, because we believe that the time between becoming infected and then going on to infect others is shorter," Professor McLaws said.

The latest data - up to Sunday - shows the postcodes with the most COVID-19 cases in the Hunter include 20 in 2285 [Cardiff, Edgeworth, Glendale],13 in 2323 [East Maitland, Maitland, Metford], 12 in 2299 Lambton, Jesmond, North Lambton], 11 in 2321 [Morpeth,Gillieston Heights, Woodville] 10 in 2287 [Wallsend, Fletcher, Birmingham Gardens] and 7 in 2307 [Shortland]. [These are examples of suburbs within each postcode, not necessarily those with COVID cases].

University of Newcastle viral immunologist, Associate Professor Nathan Bartlett, said the Hunter was better placed to contain the virus than Sydney, with fewer people and more space between people.

Dr Bartlett said the virus was "spreading most efficiently" in areas with more people living closer together.

"We're getting seeding events in the Hunter, but it seems that it's being contained at these points," Dr Bartlett said.

"We're not talking about high-density apartments like you see in south-west Sydney, with people crammed into houses."

Multiple family members living together in small houses can lead to "explosions in cases".

"I think we have a very different situation in the Hunter," he said.

Young people had been spreaders of the virus in the Hunter and they "do move around and socialise a lot".

"But it seems to be much easier to contain because they can be isolated."

Dr Bartlett believed families were the big spreaders, whether they were vaccinated or unvaccinated.

Spread among families was happening at a "far greater and aggressive rate" among dense populations with high rates of unvaccinated people, such as in south-west Sydney.

But even in the UK, he said vaccinated families were spreading the virus among each other. These people were mostly getting mild or no symptoms.

"The vaccine is certainly protecting them from severe disease," he said.

But when they do become infected, it's almost always because someone in the family has brought it home."

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