Sydney will be locked down for an extra four weeks as New South Wales records ...

Sydney's stay-at-home lockdown has been extended for another four weeks to stem the spread of the highly-contagious Delta strain of Covid-19.

Premier Gladys Berejiklian announced the lockdown extension on Wednesday morning as she announced another 177 cases of the virus had been recorded overnight. 

She said 46 of those cases were infectious in the community. 

NSW Health also confirmed the death of a woman in her 90s at Liverpool Hospital in Sydney's south-west; there are now 11 fatalities across the state linked to the latest outbreak of the Delta variant.

Ms Berejiklian on Wednesday announced she was also ring-fencing three more local government areas - Parramatta, Campbelltown and Georges River - in an attempt to contain the virus' spread. 

The decision to extend the lockdown was reportedly made in crunch crisis talks on Tuesday night after 172 new cases were announced earlier in the day. 

NSW Health flagged a further 49 venues in a late-night public health alert on Tuesday, including 13 supermarkets.

While the west and southwestern suburbs remains the epicentre of the highly contagious Indian Delta outbreak, the focus is now shifting to new areas that had so far been largely unaffected.

There were over a dozen exposure sites listed on the Northern Beaches, three on the North Shore, six in the Inner West and two in Sydney's Sutherland Shire.

The new venues of concern were announced amid concerns the state's 'gold standard' contact tracers are struggling to cope with the Delta strain.

As of Monday 14,000 close contacts were in isolation, double the number from three weeks earlier, with 7,500 of those linked to two sites.

A potential super-spreader event at Belrose Woolworths on the Northern Beaches has put 5,000 shoppers in isolation, while 2,495 close contacts so far have been linked to the Campsie Centre shopping mall in the city's south-west.

Among the venues exposed are four Coles, seven Woolworths, four Bunnings, a McDonalds, an organic bakery and even a skatepark.

It comes as Sydney recorded a new record high for this outbreak of 172 cases, bringing the total number of infections to since the outbreak began last month to 2,397 - with 79 new worrying mystery cases.

With such spiralling numbers there are now fears that the state's contact tracers are overwhelmed after a woman was told she was a close contact four days after the Campsie Shopping Centre was exposed to the virus for an 11-day stretch. 

Of most concern to contact tracers is three venues where Covid transmission has occurred.

Anyone who visited the Madhouse Bakery in Chullora, Sydney's west, on July 21 between 8am to 6pm is considered a close contact and must immediately get tested and self isolate until they receive a negative result.

It is the same story for anyone who attended Bankstown Westpac on July 19, 21, 22 and 23 and for the Flower Power Garden Centre in Terrey Hills on the Northern Beaches from 2pm to 3pm on July 19.  

The Northern Beaches has largely been unaffected by Sydney's latest outbreak, which began in the eastern suburbs and has spread dramatically though the city's west.

But now Narrabeen Bunnings has been put on high alert, along with Warriewood Eleven11 and Dee Why Ampol. 

Three venues in North Curl Curl were also flagged with Curl Curl Bacino Espresso and the North Curl Curl News agency all listed.

Manly Vale Skatepark was hit with a public health warning, as well as Terrey Hills Golf Paradise. 

The trendy Mosman Grain Organic Bakery on the Lower North Shore was also flagged, along with a McDonald's and Woolworths in Gordon.  

Bundeena IGA and The Grocery Store in Miranda in Sydney's Southerland Shire were also issued public health alerts along with a string of venues in the inner-west.

Greater Sydney, the Blue Mountains, Shoalhaven, Central Coast and Wollongong have been in lockdown since June 26, but coronavirus cases across the state have only grown - with more and more infectious in the community every day.

Countless people have been unable to work across multiple industries, as the NSW government struggles to contain the spread of the Indian Delta variant of the virus, especially in southwest Sydney.

But one welcome change yet to be confirmed is whether construction work will recommence on Saturday, with a number of safeguards and capacity limits set to be put in place. 

Workers are also tipped to undergo strict testing to ensure they are not on job sites while infected with Covid-19. 

However, tradesmen from Sydney's south-west and west – the areas hit hardest by the virus – still won't be able to work.

The lockdown extension follows a meeting earlier on Tuesday by the NSW crisis cabinet team, which also confirmed a new 'bubble' system for single residents in Sydney. 

Single Sydneysiders will now be able to meet up with a friend indoors as part of a new 'bubble' system.

It has been designed to combat mental health concerns during lockdown. 

Deputy NSW Premier reportedly John Barilaro argued against the system, while Customer Services Minister Victor Dominello was a vocal supporter.

Health Minister Brad Hazzard and NSW treasurer Dominic Perrottet also backed the bubble concept for those without significant others.

Ultimately, mental health concerns won out against possible mobility risks. 

Other changes stemming from Tuesday's meeting include a possible tweak of HSC exams for students and financial support for workers during the lockdown.  

All essential workers across the city may also be asked to take daily rapid Covid tests, with workplaces and homes still the biggest areas of transmission. 

FIND THE LATEST EXPOSURE SITES NEAR YOU

It comes as new reports emerge that NSW Health contact tracers, one deemed Australia's 'gold standard', are now overwhelmed by the flood of new infections. 

One woman who visited Campsie shopping Centre, which was exposed to the virus for 11 days, was informed she was a close contact four days after the alert was sent out - with not every Sydneysider guaranteed to be across the nightly social media alerts for exposed venues.

While contact tracers were quick to instruct staff members of the situation and that they need to self isolate, shoppers were left in the dark.  

'We found the time lag from when my wife had attended the supermarket to when we were being notified a bit concerning, particularly as the information had been circulated on social media earlier, which we ignored,' Justin Leach, who is currently in isolation with his wife, told ABC's 7.30. 

'So we were concerned at the delay.'