Hope as we get closer to identifying how Covid's Delta strain got into New Zealand.

Our cases are a likely match to a recent returnee who flew in from Sydney on August 7.

They tested positive two days later and transferred from the Crowne Plaza MIQ to Jet Park quarantine.

Prime Minister Jacinda Ardern says it's reassuring the variant's been in the community for a ‘relatively short’ time.

Auckland University Professor and epidemiologist, Rod Jackson agrees.

However cases in New South Wales are continuing to grow by hundreds daily, and Jackson says it proves Delta is a much bigger beast to beat.

He says the rate of infection as opposed to the original variant is hugely different.

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