Virus fragments were detected at both sites on the Mid North Coast earlier this week.

Sewage surveillance on Monday, and again on Wednesday, produced two positive results.

Mid North Coast Local Health District (MNCLHD) chief executive Stewart Dowrick said while today's test result is encouraging, the region is not out of the woods given the increasing concern in the Hunter region.

A drive-through testing clinic has opened at Lake Cathie sporting fields to increase the testing volume. On the first day more than 200 tests were conducted.

Yesterday, more than 900 COVID tests were completed across the region and Mr Dowrick encourages anyone with the mildest of symptoms, or who have been in areas of concern, particularly the Newcastle and Hunter region, to present for a test and comply with public health orders.

NSW reported a record 291 cases today.

Newcastle and parts of the Hunter are now in lockdown. The seven-day snap lockdown was called after five new positive cases turned up in Newcastle and eight more were found in the Central Coast region.

Newcastle, Lake Macquarie, Maitland, Port Stephens, Singleton, Dungog, Muswellbrook and Cessnock will be subject to stay at home orders until Friday, August 13.

The public health order applies to all people who live in these areas, or have been there on or after July 31.

The rules for these areas are the same as those already in place across Greater Sydney, including the Central Coast.

"The situation in Newcastle is concerning. There are many traditional connections between the Mid North Coast and the Hunter regions including a lot of students who attend Newcastle University," Mr Dowrick said.

"I ask that everyone who is subject to a public health order to comply and anyone with symptoms to go and get tested. We need to keep up this level of vigilance and work as a community to get through this."

Mr Dowrick said a rigorous testing regime will continue at the wastewater treatment plants in the MNCLHD region. He said there could be many reasons why two positive test results were returned.

There have been no sewage detections in samples taken at the district's three other testing sites - Port Macquarie, Dunbogan and South West Rocks.

There are no positive cases of COVID on the Mid North Coast. The region has been COVID free for more than 465 days.

"Detection of virus fragments in sewage can be due to shedding of the virus by someone who may have previously had the illness and may no longer be infectious. It can also be the result of a person with COVID-19 who may have visited the community and has since left the area," Mr Dowrick said.

"As well as being present in stools, viral fragments can enter the sewer when washed off hands and bodies through sinks and showers.

"Usual sewage treatment processes inactivate, or kill, the COVID-19 virus.

"We strongly encourage residents and visitors in the area to remain vigilant and get tested at the first sign of illness."

Symptoms of COVID-19 can include a runny nose, scratchy or sore throat, cough, fever, shortness of breath, headache, tiredness, loss of taste or smell, nausea, diarrhoea or muscle aches.

Last month, a COVID-positive person from Sydney visited several sites in Coffs Harbour forcing the shutdown of the Hoey Moey pub and a construction site with all close contacts sent into isolation for 14 days.

A mass testing clinic was quickly established at the Coffs Harbour International Sports Stadium and sewage surveillance was ramped up.

Two men who later travelled home to Sydney with the infected person subsequently caught the virus.

The Mid North Coast Local Health District has experienced increased COVID-19 testing since the Bondi cluster began in mid-June.

A full list of clinic locations and opening hours are listed on the NSW Government website at COVID-19 testing clinics.

The NSW Sewage Surveillance Program tests untreated sewage for fragments of the COVID-19 virus at 60 sewage treatment plant locations across NSW.

Sewage testing has been an extra level of surveillance in the Port Macquarie and Coffs Harbour regions since October 2020.

Testing sewage can help track infections in the community and provide early warning of an increase in infections. These tests provide data to support NSW Health's response to COVID-19.

An infected person can shed virus in their faeces even if they do not have any symptoms, and shedding can continue for several weeks after they are no longer infectious.

NSW Health says there are several different situations that could be occurring when fragments of the COVID virus are found in the sewage.

It could mean there has been one or more people who are infectious with COVID-19 in the catchment area; someone has recovered and is no longer infectious; or a person with COVID might have visited the community and has since left the area.

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