Covid-19 coronavirus: Melbourne man who travelled to NSW likely source of outbreak

New South Wales authorities say that a man from Melbourne who travelled on June 30 has been identified as the likely source of the coronavirus outbreak at the Crossroads Hotel in Sydney.

The state's chief coronavirus "detective" Jennie Musto, who manages the team tracing infections, told reporters today the most likely source of the Crossroads outbreak was a Melbourne man who came to a workplace in Sydney.

She said that the workplace was a freight company, although the man was not a truck driver.

"About six" of his colleagues were also infected with the virus.

The man and several of his colleagues later went to the Crossroads for a party on July 3, this led to an outbreak at the hotel, which is now linked to at least 34 cases.

"The man from Melbourne didn't think he was particularly unwell, didn't think he was sick with Covid, he travelled on the 30th of June, he's been in NSW for a while and it wasn't until we interviewed him and his colleagues with more detail that we made the link that they were all on the Crossroads on the 3rd of July," Musto said.

Authorities are not releasing details of the workplace but say there is no risk there.

NSW recorded 13 new cases of coronavirus, NSW Health Minister Brad Hazzard confirmed.

"Don't get an expectation that it (case numbers) will always be zero because we think this virus will continue to transmit slowly," he said.

"We will have transmission from time to time and that's just the way it is."

Of the new cases, three were in hotel quarantine and 10 are linked to the Crossroads Hotel – six of those actually attended the venue and the other two are close contacts.

Two males, aged 24 and 27, acquired the infection at the Planet Fitness Gym in Casula where there was one previously identified case.

More than 17,000 tests have been conducted in NSW during the last 24 hours.

The deadly virus has spread rapidly through the area forcing a number of establishments to close including a nursing home, a Kmart store, various pubs and a gym.

The Picton Hotel was closed for deep cleaning after a patron who used the gaming room tested positive.

The Wests League Club and the Macarthur Tavern, in the southwestern suburbs, also closed overnight after infected customers visited during the weekend.

NSW's Chief Health Officer Dr Kerry Chant said she is concerned about people who may have travelled to NSW from Melbourne before the borders closed.

"We are very concerned about areas where we may have had a number of visitors from Melbourne and the Mitchell Shires. Particularly in our coastal areas and border communities we need to have high rates of testing so if there's been any seeding we can mop it up," Chant said.

"The Crossroads highlights we won't gain control of this if we don't have people on board."

She said it will take at least two weeks to understand if the state has managed to stem the spread of Covid-19 throughout the southwest.

"We need a period of high testing rates to ensure we've stopped it," she said.

Chant also warned residents to be cautious when visiting aged care facilities.