Both cases, a woman in her 30s and a woman in her 60s, are close contacts of the man in his 30s from the Port Stephens area, announced last week.

They have both been isolating at home since they were identified as close contacts, so there is no ongoing risk of community transmission.

HNEH public health physician, David Durrheim said while there was no ongoing risk, this had shown just how quickly the virus could spread.

These latest cases takes the cluster to six, all isolating at the time.

"The situation in Sydney is on a knife-edge and we urge anyone who is planning to go to Sydney for non-essential reasons to reconsider and not travel," Dr Durrheim said.

"We also urge Sydneysiders not to travel into rural NSW.

"We have seen in Sydney there are particular high risk venues, pubs, clubs, restaurants, places of worship and gyms, places where people congregate and these are dangerous places to be at this point in time."

Premier Gladys Berejiklian this morning announced that gyms would now be required to have a COVID safety plan in place and hygiene marshall on shift at all times, even at 24-hour venues which sometimes operate without staff.

"I also want to stress the importance of social distancing," she said.

"The 1.5 metres has to be part of our lives for the duration of this pandemic.

"And if you can't maintain social distancing, you should be wearing a mask."

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