Covid 19 coronavirus: Government keeping 'an open mind' to source of Valentine's Day outbreak says Associate Health Minister Ayesha Verrall

Infectious diseases expert and Associate Health Minister Ayesha Verrall says the Government is keeping an open mind to the source of the Valentine's Day outbreak.

And because genomic testing hasn't linked the Auckland family's cases to a returnee from MIQ that reduces the chance of undetected community transmission that "escaped" somehow, Verrall told the Herald.

If it was connected to a returnee that would mean there was an undetected chain of transmission through the community which led the mother to be infected.

"That is reassuring but of course we continue to do all our double-checks by doing community testing and we encourage anyone with symptoms to get tested."

The advent and implementation of sewage testing will also help officials gauge whether there has been wider community transmission.

Officials were also tracing the father and the daughter to see whether there was a chain that infected the mother "in the other direction".

"It's really important that we don't focus on just one theory - that we keep working on multiple theories.

"That we keep looking at her workplace even though there is regular testing at that workplace to make sure there aren't any other sick people there or any other avenues where it might have been transmitted through the environment."

Cabinet decided to go to alert level 3 before the genomic testing results were back out of an "abundance of caution" that it was the more infectious strain.

"I think it's important we take these three days to really assess where we're at and yes, I am relieved that we're at level 3 when I found out that it was the UK variant because we know it is more infectious."

Verrall said after finding out the outbreak was the UK variant - which is about 50 per cent more infectious than other variants - she had a sense of relief that Auckland was in lockdown.