A fourth person has returned a positive coronavirus test in Sydney, as NSW authorities confirm the state's first case of the contagious Delta variant.
Premier Gladys Berejiklian on Thursday morning said a 70-year-old woman who was at the Bell Cafe in Vaucluse has tested positive for the virus, as had a man in his 40s from the Baulkham Hills area who is not yet linked to any existing exposure sites.
However, authorities are still determining whether his case is old or a false positive, as the viral load in his system was very low.
It comes after two new cases were found on Wednesday - a man in his 60s who worked as a driver transporting international flight crew, and his wife.
The man's infection has been confirmed to be the state's first of the Delta variant, first discovered in India. His viral sequence does not match anything on Australia’s records but fits "perfectly" with one uploaded from the US.
Police are investigating whether the man was wearing appropriate PPE while working and whether he was vaccinated.
Ms Berejiklian said people in Sydney's eastern suburbs should refrain from going to large gatherings, practice good hygiene, and be "extra careful" in the coming days.
"At this stage, we're all on high alert," she told reporters.
"We're asking people to modify their activity, to consider where they've been, what their movements have been and what their movements may be until we go through the next few days, as the situation is evolving."
A new health alert, meanwhile, has been issued for a fruit grocer in Leichhardt in Sydney's inner west, joining more than a dozen exposure sites that have now been identified across Sydney. Alerts were also issued last week for venues in various regional NSW towns after an infected couple from Melbourne drove through on their way to Queensland.
An updated list of exposure sites can be found on the .
Western Australia, South Australia and Tasmania have now closed the border to anyone who attended virus exposure sites.
Cars line up for COVID-19 testing at Bondi in Sydney, Thursday, June 17, 2021. Source: AAP
On Thursday evening Victoria announced residents from the City of Sydney, Waverley and Woollahra council areas would need to obtain a travel permit, get tested and isolate until they received a negative result before being allowed to enter the state.
Ms Berejiklian urged anyone “with even the mildest of cold-like symptoms” to come forward for testing and isolate until a negative result is received.
She said the new cases - the first local infections in NSW since early May - were a reminder of the need to be vigilant.
"We can't be complacent," she said. "We know that two [cases] can become 20 very quickly."
There were 23,145 tests in NSW reported to 8pm on Wednesday and 16,425 COVID-19 vaccines were administered.
Investigations are also continuing into the source of a COVID-19 case diagnosed in hotel quarantine, which has an identical viral sequence to two cases who were staying in an adjacent room at the Radisson Blu hotel in Sydney's CBD.
