Either someone passing through, or someone living in the area has COVID-19 and there is no way of knowing which strain, Hunter Public Health Physician David Durrheim said on Wednesday.

"Now is the time where we have to hunt the virus down, we have to flush it out," Dr Durrheim said.

It comes just days after 5,500 vaccinations were diverted from the Belmont Vaccination Hub to Year 12 students living in Sydney hotspots so they could complete their exams .

Now the heat is on in the Hunter, including for the 115,000 people living in suburbs serviced by the Belmont sewage treatment plant.

Health officials are holding their breath and counting on tests and contact tracers to find any positive cases and minimise the risk of widespread infection.

So far there are still no confirmed cases of COVID-19 in the Hunter but there is no such thing as a 'false positive' with sewage detection tests, Dr Durrheim said.

Together with NSW Chief Health Officer Kerry Chant, Dr Durrheim issued an urgent call to Novocastrians with symptoms to get tested immediately.

Dr Durrheim also called on people to consider limiting their movements.

"I think personally that we should all be restricting our movement at this point," he said. "Even though we are not under a stay-at-home order, we should really try to starve the virus of any opportunity of spreading. People should be asking themselves, 'Do I really have to work in the work place or can I do it at home? Can I limit the amount of travel from my home? Can I limit my exercise to nearby? Can I limit the amount of shopping I do'?

"At the moment we just don't know how much or how many people could be infectious. We need to be super vigilant, and limit our movements and our engagements."

"Every single one of us that has a sore throat, runny nose, shortness of breath, chest pain, or a fever, don't hesitate, immediately go and get tested, go home, and isolate - don't take the virus out in the community until you get a negative result. You have got to prove that it is not COVID-19."

He also predicted that Novocastrians would heed that call, and asked that they exercised patience as testing centres moved to extend their hours.

"We know that all people are doing the right thing - testing centres are very full and they are extending their hours - and then go straight home and isolate until they get a result."

As he predicted, testing centres were swamped on Wednesday with traffic controllers redirecting people away from queues outside the University of Newcastle hub, and reports of long queues outside other testing centres.

However, a NSW Pathology spokeswoman said on Wednesday the operating hours of the testing clinic at the university had been extended. It will be open from 7.30am to 5pm, seven days a week until further notice.

"The John Hunter laboratory is also ramping up its testing capacity to accommodate a potential increase in demand," she said.

A full list of up-to-date operating hours for Hunter test sites is available on the Hunter New England and Central Coast Primary Health Network website.

The "high viral load" was found in samples taken on Monday and which were returned positive late on Tuesday night for three Hunter sewage treatment plants - Shortland, Burwood and Belmont, which service the suburbs of Greater Newcastle, Lake Macquarie and southern Port Stephens.

NSW Premier Gladys Berejiklian said the rates of the virus detected were very high, pointing to "undetected cases up around the Hunter area."

NSW recorded 233 new locally acquired cases in the 24 hours to 8pm on Tuesday, with 103 linked to a known case or cluster - 79 are household contacts and 24 are close contacts.

Chief health officer Dr Kerry Chant said health authorities were "very concerned" by the Hunter testing results. She named Birmingham Gardens, Shortland, Maryland, Fletcher, Minmi, Cameron Park, Stockton and Fern Bay among the suburbs flagged as priorities for testing for anyone with even the mildest symptoms as efforts continue to work out where the shedding has come from.

Together, the three treatment plants cover a population of more than 400,000 people, but the area of most concern and with the highest levels of viral load was that serviced by the Shortland treatment plant, which takes in a population of 60,000 people.

Hunter residents and the region's MPs have pointed to loopholes in the Public Health Orders as being behind the development. Among them Newcastle MP Tim Crakanthorp who slammed loopholes allowing food van operators and rideshare drivers to travel to work in the Hunter, and Sydney people coming to local open houses, as well as the pause in July on Greater Sydney construction which saw local crews removed from jobs as Sydney crews were relocated out of lockdown areas.

"Time and time again I have raised these Public Health Order loopholes with the NSW Government, and time and time again I have been fobbed off," he said. "Our city has been on a knife's edge for the last six weeks because of this government's failure to step up. They know what the issues are and they need to outline what they will do to fix them."

Shadow Minister for the Hunter Yasmin Catley said residents were "losing confidence in this government's capacity to vaccinate the community". "Five days ago people were getting text messages cancelling their vaccine appointments [at the Belmont hub]," said Ms Catley, who is the MP for Swansea.

"Then today, the chief health officer [Dr Kerry Chant] stands up and says the sewage detection is very concerning and worrying in the community and she's telling people to get tested. The mixed messaging that is coming out of the government at the moment is causing such confusion in the community."

NSW Premier Gladys Berejiklian has said that once 50 per cent vaccination rates are reached, some lockdown laws could be relaxed, but the region is not moving quickly to reach that target.

"This community has very low vaccination rates, comparatively," Ms Catley said. With Pfizer vaccines being taken from the Belmont hub, she expected the region's vaccination rates to stay "similar to what they are".

The Newcastle Herald reported on Thursday that the Hunter Valley had some of the lowest COVID-19 vaccination rates in Australia. In the Hunter Valley, excluding Newcastle, about one in seven people aged 15 and above - or 14.1 per cent - are fully vaccinated for COVID-19.

Vaccination rates are only slightly higher in Newcastle and Lake Macquarie, with 17.7 per cent of people aged 15 and above fully vaccinated, and 41.3 per cent partially vaccinated.

The current turn-around time for test results conducted at public test sites is less than 24 hours, a NSW Health Pathology spokeswoman said, with 90 per cent of patients receiving their results in less than 30 hours. "Positive COVID-19 results are always reported immediately to the referring doctor and public health unit," she said.

The COVID-19 testing prioritisation protocols which have been in place throughout the pandemic, giving priority to frontline workers, will continue, she said. "As a measure to maintain essential services, if a person identifies as a healthcare worker at the time of testing, their sample will be marked as high priority."

Dr Durrheim said from here, the best case scenario was that either someone living locally is identified before they infect other members of the community, or someone who has visited the area can be traced back to where and when they were here.

"It's either very mobile visitors or it's multiple visitors or it is people who are travelling because they have reasonable excuse, such as ... travelling for work," he said. "But we really cannot exclude that there could be local transmission and even if it was visitors, we have no idea if they might have infected someone else."

IN THE NEWS:

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: