The latest confirmed Hunter case is a 34-year-old man who recently returned from the Middle East.

The returned traveller tested positive for COVID-19 while in hotel quarantine in Sydney.

Public health physician Dr David Durrheim said the Sydney outbreaks are "a real reason for concern".

"We would strongly advise anybody from the Hunter New England region to rather stay at home than visit Sydney at this stage unless absolutely necessary.

"This virus, if you give it half a chance, can spread very, very rapidly and even from asymptomatic people in the pre-symptomatic stage before they develop symptoms.

"Our only defence is really standing back and making sure that we take real care with our hand washing and not taking coughs and colds into the community and spreading the virus.

"If you have been tested in the past, a single negative test does not mean if you develop new symptoms that you are COVID-free.

"It's very important to again go and get yourself tested.

"The good news is that the new testing regime, which includes a deep nasal swab rather than a nasal-pharyngeal swab is much more comfortable.

"We encourage anybody who develops even mild symptoms - a scratchy throat, a runny nose, a mild fever, a cough - get yourself tested and make sure you don't have COVID-19 and let's make sure we keep our community safe against this virus."