Patient zero behind Sydney's coronavirus outbreak may never be found

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Mystery continues to surround the original source of Sydney's growing coronavirus cluster with health authorities conceding it may be a challenge 'beyond them'.

Another 30 new cases were recorded on the city's Northern Beaches on Sunday as the cluster grew to 68.

Around 270,000 residents along the peninsula are in lockdown until at least Wednesday night as a string of temporary restrictions were re-introduced on the rest on Sydney. 

While all of the latest cases are directly linked to the Northern Beaches, NSW Health contact tracers are still scrambling to track down the source of the outbreak that has ruined Christmas plans for many Australians.

© Provided by Daily MailThe coronavirus cluster on Sydney's Northern Beaches has grown to 68. Pictured is a local resident getting tested at a drive-through clinic on Sunday

Genomic sequencing suggests the virus strain associated with the cluster is most closely linked to a female returned traveller who arrived into Sydney from the US on December 1 infectious before going into hotel quarantine.

But with no explanation as to how it escaped and seeped into the Northern Beaches, the extensive investigation has been ramped up.

'There is no-one else we have identified that could be the source,' NSW chief health officer Kerry Chant told reporters on Sunday.

'At the moment we are forensically looking at all of the journeys of that individual to see if there were any points associated with it.

'There is an intensive investigation underway and while a really do want to find the source, it may be that this is going to be a challenge beyond us.

'We are trying to find the earliest possible case and then link that back to anyone that may have come in contact with this individual. 

'We have to keep an open mind because there may be an unknown source.'

© Provided by Daily MailA string of temporary restrictions have been re-introduced on Greater Sydney as the Northern Beaches cluster grows. Pictured are women disembarking a ferry at Manly on Friday.

© Provided by Daily MailThe weather and advice  from authorities to stay at home left Manly's usually bustling beachfront (pictured) deserted on Saturday, hours before the region went into the lockdown

Contract tracers are pouring over CCTV footage in a desperate effort to track down the original source. 

'We have set up a team and are following. at any one time, 10 or 20 lines of inquiry and we pursue them all concurrently,' Dr Chant said.

'There is no one who wants to get to the bottom of this more than myself because if I understand the clear chains of transmission I can then better inform government about the risk.

'The problem we have at the moment is that I do not know how we got there so I do not know the person nor where that person has been.'

© Provided by Daily MailNSW health chief Dr Kerry Chant (pictured on Sunday) admitted tracking down the original source may be a challenge beyond health authorities

Dr Chant was adamant no one who has been granted quarantine exemptions, including international flight crews had tested positive for the virus.

Health minister Brad Hazzard added: 'There is no case whatsoever of any positive case from the process.'

'The only missing link here at the moment is who was the original source of that overseas virus.' Premier Gladys Berejiklian tightened restrictions for Greater Sydney and the Central Coast amid fears the outbreak will spread.

From 11.59pm on Sunday until 11.59pm on Wednesday all Greater Sydney residents can only have a maximum of 10 people in their homes.

There are also new restrictions for venues including a 300 person cap, a one person per four square metre rule and a ban on singing and dancing. 

© Provided by Daily MailThere was also a massive queue for testing in the eastern suburbs at Bondi on Sunday