'Brace yourselves': Gladys Berejiklian warns Sydney to expect an explosion of new coronavirus cases today - as desperate search for 'patient zero' who spread overseas strain continues

Sydney is bracing for an explosion of coronavirus cases as contact tracers scramble to contain the Northern Beaches outbreak.

About 270,000 locals are effectively in lockdown for the next three days after 17 new cases were recorded within 24 hours in the area on Thursday.

Genomic sequencing results show the latest outbreak is an overseas strain, but health authorities are still trying to track down the source. 

Premier Gladys Berejiklian warned the number of cases would definitely rise on Friday as testing across Sydney's northern peninsula ramps up.

'I do want to ask everybody to brace themselves, we are going to definitely have more cases today,' she said on the Today Show. 

'The number of people that were at the RSL event on December 11 and then the bowling club the following Sunday were substantial and then they’ve got household contacts and contacts of theirs.'

A desperate search is underway to find the source of Sydney's latest coronavirus outbreak after another locally transmitted case was recorded (Pictured: Nurse Rebekah Duffy conducts COVID-19 tests at the Bondi Beach testing clinic)

Ms Berejiklian urged residents from Spit Bridge to Palm Beach to stay at home until Sunday while urgent testing and contact tracing continues.

'We don’t want the disease to spread more broadly throughout Sydney, so we’re asking everybody to think about what they’re doing and to monitor their behaviours,' she told Sunrise.

'We want people to have a good Christmas, but we know this has really unfortunately disrupted many plans.

'Our aim is to really get on top of this as soon as possible so people can have as less disruptive Christmas as possible.

'The next two to three days will be incredibly critical.'

Northern beaches residents from The Spit Bridge to Palm Beach are advised to work from home and not to visit elderly relatives.

They are also urged to avoid unnecessary gatherings, keep to household groups and avoid unnecessary travel, including travel to high-risk venues like restaurants, cafés and bars.

A long queue had already formed outside the Mona Vale clinic before it had opened on Thursday morning

'As a number of new cases are currently being interviewed, it is likely that a number of new venues will be identified and that people in the northern beaches may have ­attended these venues,' a NSW Health statement read. 

The outbreak has been linked to several venues across the city after a drummer in his 60s performed at the sites, including Avalon RSL Club, Penrith RSL and Kirribilli Club, while infectious. 

An infected couple from Avalon who refused to self-isolate after getting tested for coronavirus were also at the Avalon RSL club on December 11. 

It's also understood the aged care worker may have contracted the virus after crossing paths with the woman in her 60s at a nearby bowling club in Avalon. 

Health authorities are racing to contain the mystery cluster which began to escalate on Thursday.

NSW Premier Gladys Berejiklian urged any residents in the northern beaches with the 'mildest of symptoms' to get tested as soon as possible

Premier Gladys Berejiklian said the figures will definitely rise on Friday as testing across Sydney's northern peninsula ramps up

Northern Beaches Council has temporarily closed all community facilities until Sunday to coincide with the stay at home orders.

They include skate parks and playgrounds, community sporting activities in parks and reserves, outdoor gyms, public swimming pools, community centres and libraries.

'We will maintain all essential services like waste collection, childcare, Meals on Wheels, road maintenance as well as customer service online and on the phone,' the council posted on Facebook late Thursday.

Two other venues his band visited, Penrith RSL and Kirribilli Club, have been put on alert as well amid fears he was infectious when he performed. 

NSW chief health officer Dr Kerry Chant said investigations are underway to track down the source of the infection, which has been linked to the Avalon RSL club.

Dr Chant has urged anyone who was at the club at any time on December 11 to come forward for testing.

VENUES ON HIGH ALERT 

 People who have visited the following Northern Beaches locations should get tested immediately and isolate until they receive a negative result, and until they have been contacted by NSW Health:

· Woolworths Mona Vale, 25/29 Park St, Mona Vale, 13 December, 12-12.30pm

· Aldi Mona Vale, 13 Bungan St, Mona Vale, 13 December, 12.45-1.30pm

· Avalon Beach Surf Life Saving Club, 13, 14 and 15 December, 9-9.30am

· Palm Beach Rockpool, LOT 1 Rock Bath Rd, Palm Beach, 14 December, 9:30-10:30am

· Woolworths Avalon, 74 Old Barrenjoey Rd, Avalon Beach, 14 December 5-5.30pm

· Chemist Warehouse, 4/74 Old Barrenjoey Rd, Avalon Beach, 14 December 5.20‑5.25pm

· Commonwealth Bank, 47 Avalon Parade, Avalon Beach, 15 December, 12-12.15pm

· Mitre 10, 49 Avalon Parade, Avalon Beach, 15 December, 12-12.20pm

· Roof Racks World, 13/87 Reserve Rd, Artarmon, 15 December, 2-2:30pm

· HongFa BBQ Restaurant, Dee Why, 15 December 4.30-4.45pm

· Dee Why Fruit Market, 33 Oaks Avenue, Dee Why, 15 December, 4.45-4.55pm

· North Avalon Cellars, 4/3 N Avalon Rd, Avalon Beach, 15 December, 6-6.05pm

· Careel Bay Dog Park and Hitchcock Park, Barrenjoey Rd, Avalon, 16 December 7‑7:30am

· Palm Beach Pool, LOT 1 Rock Bath Rd, Palm Beach, 16 December, 8am-9am

· Brot and Wurst, 1442 Pittwater Rd, North Narrabeen, 16 December, 2pm-2:05pm

· Avalon Beach Post Shop, 45 Avalon Parade, Avalon Beach, 16 December 3.30-3.50pm

Avalon RSL club 11 December all day till closed

Penrith RSL club 13 December 1-6 pm

Kirribilli club 14 December 12-3 pm

· Bing Lee, Gateway, 1 Mona Vale Rd, Mona Vale – Monday, 14 December, 4.30-4.45pm

· Woolworths Avalon Beach, 74 Barrenjoey Rd, Avalon Beach – Tuesday, 15 December, 12-12.30pm

Oliver's Pie, Careel Shopping Village, 1 Careel Head Rd, Avalon Beach – Monday, 14 December, 9-9.15am

Woolworths Avalon Beach, 74 Barrenjoey Rd, Avalon Beach – Sunday, 13 December, 12-5pm

Anyone who has attended the following additional venues is considered a close contact and should get tested and isolate for 14 days even if they receive a negative result:

· Hungry Ghost Café, 20 Avalon Parade, Avalon – Sunday, 13 December, 9.30am-11am and Tuesday, 15 December 9.30-11am

· Sneaky Grind Café, 3/48 Old Barrenjoey Rd, Avalon Beach – Monday, 14 December, 9.30-11am

· Barramee Thai Massage and Spa, 4/42-44 Old Barrenjoey Rd, Avalon Beach – Monday, 14 December, 2-3.30pm

· Bangkok Sidewalk Restaurant, 1/21-23 Old Barrenjoey Rd, Avalon Beach – Monday, 14 December 7-8pm

· Avalon Bowlo (bowling club), 4 Bowling Green Ln, Avalon Beach – Sunday, 13 December, 5-7pm (not 3-5pm as previously reported) and Tuesday, 15 December 3-5pm

Palm Beach female change rooms – Sunday, 13 December 9-9.15am

Coast Palm Beach Café, Barrenjoey Rd, Palm Beach – Sunday, 13 December 10-11am

A confirmed case also travelled between the following stations on 14 December at the following times. Other passengers are considered to be casual contacts, and should get tested and isolate until a negative result is received.

· Roseville to Redfern, 6.50-7.40am

· Redfern to Milsons Point, 11.20am-11.45am

· Milsons Point to Roseville, 3.15-3.40pm