The source of the infection is under investigation, but it is believed to have been acquired outside of the region, unlinked to any previous local cases.

Contact tracing is underway and Mid North Coast Local Health District will provide more information as soon as it is available, including any potential exposure venues of public concern.

This case will be included in NSW Health's official numbers on Wednesday.

There are now four confirmed COVID cases on the Mid North Coast.

Three other people tested positive at the weekend - two at Kempsey and one in Coffs Harbour.

The Kempsey cases forced NSW Health to call a snap lockdown for the local government area, commencing today (Tuesday, September 21) at 5pm.

"We ask the community to continue to practise COVID-safe measures at all times and please remain vigilant for symptoms of COVID-19, even if mild. If symptomatic, you must isolate and have a test," MNCLHD chief executive Stewart Dowrick said.

The Kempsey local government area (LGA) will return to strict stay-at-home orders for the next seven days.

Kempsey joins regions further north to return to strict lockdown rules including the Tweed, Byron Bay and Lismore.

These stay-at-home orders also apply to anyone who has been in these affected LGAs since the following dates:

Everyone in the affected LGAs must stay at home unless it is for an essential reason, which includes:

People who are fully vaccinated can attend an outdoor gathering of up to five people for exercise or outdoor recreation, as long as all of those aged 16 or older are fully vaccinated.

To determine the extent of the risk and detect any further potential COVID-19 cases in these areas, the Mid North Coast Local Health District is calling on the communities to come forward for testing in large numbers.

A full list of COVID-19 testing clinic locations and opening hours are listed on the NSW government website at www.nsw.gov.au/covid-19/health-and-wellbeing/clinics