A COVID-19 cluster from a southwest Sydney pub continues to grow, with its "patient zero" identified as a Melbourne man who attended a party at the venue.
NSW Chief Health Officer Kerry Chant on Wednesday said there are now 34 cases linked to the Crossroads Hotel in Casula, at least 20 of them patrons.
The state reported 13 new COVID-19 cases in the 24 hours to 8pm on Tuesday, with only three of them unconnected to the hotel.
Two of the 10 hotel-connected cases attended the Planet Fitness gym nearby, meaning three gym-goers since July 4 have come down with the virus.
Two of the 34 cases to date are "tertiary" cases, or contacts of contacts.
"This highlights the rapidity with which COVID can spread and the importance of us identifying these cases very quickly," Dr Chant told reporters.
"It's very important we don't lose sight that COVID could've been introduced in any other part of Sydney ... this is a stealthy virus."
NSW Health also confirmed the "patient zero" of the outbreak was a Melbourne freight company employee who attended the Crossroads Hotel on July 3 for a work party. Six of his colleagues have since caught COVID-19.
The man entered NSW on June 30, before its border with Victoria closed.
NSW Deputy Premier John Barilaro earlier in the day confirmed genomic testing of the virus circulating in Casula found links to a strain from Victoria, where hundreds of new COVID-19 cases are being reported each day.
Victoria recorded 238 new cases on Wednesday.
Both Mr Barilaro and Premier Gladys Berejiklian have this week said localised or statewide lockdowns were undesirable and options of last resort in NSW.
The intensive care capacity in NSW hospitals had almost quadrupled since the early stages of the pandemic, which has killed 51 people in the state to date.
Dr Chant also named a number of venues where confirmed COVID-19 cases spent time including the YMCA at Revesby, Wests Leagues Club at Leumeah, Macarthur Tavern in Campbelltown and Casula Kmart.
The Milky Lane burger joint in Parramatta and the Bavarian Macarthur restaurant in Campbelltown were later added to the list.
A worker at Woolworths in Bowral has also tested positive to the virus and the store underwent deep cleaning on Tuesday night. The staff member worked at the store on July 12 and was asymptomatic at the time.
A southwest Sydney pizza restaurant, meanwhile, is closing for three days for deep cleaning after a customer on Friday tested positive for COVID-19.
Mancini's Original Woodfired Pizza at Belfield said NSW Health had deemed the case a low risk to staff as the male customer stayed within his group.
NSW Police are working with Liquor and Gaming to investigate if Crossroads Hotel breached any guidelines. All patrons of the hotel from July 3 to 10 must self-isolate and are being urged to get tested.
One of the cases linked to the hotel is a person who visited the Prestons Lodge Advantaged Care nursing home, which has been placed into lockdown.
"Don't get an expectation it will always be zero (cases) - we think this virus will continue to transmit lowly through the community and from time to time we can fully expect (this)," NSW Health Minister Brad Hazzard told reporters.
"This is a world pandemic, a one-in-100-year event."
Ms Berejiklian also on Tuesday announced a tightening of restrictions for pubs and hotels, including a cap of 300 patrons and mandatory sign-ins. Those restrictions will come into effect from Friday.
Ms Berejiklian this week also revealed use of virtual and online healthcare services had increased by 700 per cent over the four months to May.