Three new COVID-19 cases in Sydney

Two new cases of COVID-19 have been diagnosed in Sydney's northern beaches on the same day a southwest Sydney man who drives international air crew to and from Sydney airport was confirmed to have the virus.

The three locally acquired cases end NSW's 12-day streak with no local coronavirus transmission.

Health authorities do not yet know the source of the two northern beaches cases, a woman in her 60s and a man in his 70s who are close contacts of each other.

The cases were confirmed on Wednesday afternoon.

NSW is undertaking contact tracing and urgent genome sequencing, with results expected within the next day or two.

NSW Health says no links have been identified to other known cases at this stage.

Authorities are warning anyone in the northern beaches area to monitor for even the mildest of symptoms and come forward for testing immediately if they appear.

The man and woman visited several venues while infectious.

People who attended the following venues at specific times are considered close contacts and must be tested and isolate for two weeks, even if they receive a negative result: Palm Beach female change rooms, Coast Palm Beach Cafe, and Woolworths Avalon Beach on Sunday; Sneaky Grind Cafe, Barramee Thai Massage and Spa, and Bangkok Sidewalk Restaurant at Avalon on Monday; and Avalon Bowlo and Hungry Ghost Cafe on Sunday and Tuesday.

Alerts have also been issued for Oliver's Pie at Avalon and Bing Lee at Mona Vale on Monday, and Woolworths at Avalon on Tuesday.

The other new case is a 45-year-old southwest Sydney man, who drives vans ferrying international air crew. The man was first symptomatic on Saturday but did not get tested until Tuesday afternoon.

He was confirmed virus-positive on Wednesday morning.

Health Minister Brad Hazzard told reporters the case highlighted the need for the NSW government to be vigilan at the state's borders.

"We may be an island, but we are not totally isolated from the pandemic that is raging across the world."

NSW Chief Health Officer Kerry Chant said the infected driver worked only with air crew members and was not involved in regular taxi services for the public. He wore a mask while working.

The other three members of his household have tested negative to COVID-19 but will self-isolate for 14 days.

A health alert has also been issued for a children's football training session conducted by Forest Rangers FC in Peakhurst on the afternoon of December 11.

All adults in attendance at that time are casual COVID-19 contacts and should monitor for respiratory symptoms, seek testing and isolate until they get a negative result. Children should also get tested if they develop symptoms.

Mr Hazzard said at least 2000 international air crew members were touching down in Sydney each week, with turnarounds of up to 72 hours before flying out again.

While they did not have total liberty, air crew had more freedom of movement than returned travellers in hotel quarantine, who cannot leave their rooms.

Mr Hazzard said that if national cabinet did not establish a nationwide regime for arriving air crew, NSW may implement its own changes.

That would entail placing air crew in full hotel quarantine, but only until their next flight out of the country.

"Our inclination is to say to international air crews and airlines ... crews coming in to NSW will be most likely to be required to quarantine in the same way as other international visitors," Mr Hazzard said.

The driver's employer, Sydney Ground Transport in inner Sydney's Alexandria, has ceased operations while contact tracing is underway. Its staff will also be tested for COVID-19.