Greater Sydney will remain in lockdown for at least another week from Friday as NSW records 27 new cases of Covid-19.
Premier Gladys Berejiklian confirmed the lockdown extension this afternoon, saying the decision was based around the number of cases who have been in the community while infectious.
She said it was "unfortunate" that just 13 of the state's new cases were in isolation for their full infectious period.
The lockdown will now be in place until midnight on July 16 for Greater Sydney, the Central Coast, the Blue Mountains, Wollongong and Shellharbour.
Berejiklian said the Delta Covid-19 strain circulating in NSW is a "game changer".
"The reason why the New South Wales government has taken this position is because we don't want to be in a situation where we are constantly having to move between lockdown, no lockdown, lockdown, no lockdown," she said.
"What we want to do is give us our best chance of making sure this is the only lockdown we have until the vast majority of our citizens are vaccinated."
Berejiklian warned that tomorrow's case numbers are likely to be even higher than the 27 infections announced today.
"I can foreshadow overnight that we've had a number of cases, more than we would like to have seen," she said.
"So I'm anticipating that tomorrow's number will be higher than what we have seen today but they are at the moment concentrated in three local government areas."
'A lot of spread' in NSW - Bloomfield
NZ's director-general of health Ashley Bloomfield said "it was quite clear there had been quite a lot of spread" in NSW at today's 1pm press briefing.
Covid-19 Response Minister Chris Hipkins said he was in the process of reviewing 500 MIQ rooms still available to people travelling from Australia and would make an announcement next week.
Berejiklian met health officials yesterday to determine whether or not the state, which has been struggling to contain its case numbers, would remain under lock and key.
The lockdown extension means students in Greater Sydney will be learning online when school starts back on Tuesday, but regional NSW students will return to face-to-face learning.
NSW recorded 35 new cases on Monday — an equal daily high — and 18 new cases yesterday. Two of those cases were in the community for their entire infectious period and five were isolated for only part of their infectious period.
The lockdown impacting Greater Sydney was due to end at 11.59pm on Friday, July 9, but Berejiklian told reporters yesterday the lockdown "is having its desired effect to date … but it is still concerning that a number of cases are remaining infectious in the community".
"We're looking at a scenario where we don't burden our citizens more than we have to but we also have to accept the new world we're living in," she said.
"This Delta strain is likely to be the dominant strain of the virus until we have further information.
"We intend for this lockdown to be the only lockdown we go through, and that will factor into our decision making."
Problematic for the state is the Summit Care aged care facility in Baulkham Hills, which had a rise of cases yesterday, along with an illegal house party at Meriton Suites, which has resulted in 12 new cases.
Urgent Covid alert at Sydney Opera House
The Sydney Opera House is on high alert after a subcontractor worked at the iconic building for six days while potentially infectious with Covid-19.
The site was being deep cleaned on Wednesday morning and has been closed since June 26, in line with the citywide lockdown.
A spokeswoman for the Sydney Opera House said it was informed by the health department that the subcontractor who worked between July 1 and 6 had returned a positive swab.
"NSW Health is currently undertaking its investigations, and the Opera House is taking all necessary steps in line with its Covid Safety Plan," the spokeswoman said.
"In line with the current stay-at-home orders, the building has been closed to the public since Saturday June 26."
It is unclear whether they were infectious for the entire six-day period.
NSW Police said there were no Covid-related breaches associated with the Opera House.
It is believed workers were classed as essential and were allowed on site to set up for a new and upcoming performance.
Numbers critical over the next few days - expert
Professor Peter Collignon, an infectious diseases physician and microbiologist, told The Project on Tuesday night it was "likely" the lockdown would be extended for a few days, but that the case "numbers over the next few days will be critical".
Collignon published a paper yesterday, Covid-19 and future pandemics: is isolation and social distancing the new norm?, in which he said the "new norm is isolation, plus social and physical distancing, and this new norm will likely be with us for some time to come".
Collignon warned "this is the peak danger period for spreading viruses" and urged the Government to maintain restrictions "even if you don't have any Covid spread in the community".
"I don't think we can live life normally for the next four months, we need to accept there will be restrictions, still get on with life but not go back to 2018, 2019. I don't think that's safe until at least October, November," he said.
NSW's chief health officer Dr Kerry Chant also revealed there were 26 hospitalised Covid-19 patients: six in intensive care and two being ventilated.
"The ages of those in ICU is one in their early 50s, one in the early 60s, three in their 70s and one in their 80s," she said.
"This is a salient reminder that Covid can have an impact on you and your loved ones.
"Please as you move about the community, assume everyone has Covid, follow the public health advice, and please minimise your exposures to others, particularly in indoor settings."