Health authorities are urgently trying to find the missing link which led to an Auckland woman contracting Covid-19.
This morning, Covid-19 Response Minister Chris Hipkins said preliminary testing showed a link between the woman's positive test and the November quarantine cluster.
But exactly how it was passed from that cluster, which centres on two Defence Force workers, and the woman in her 20s has not yet been established.
So what are some of the possible sources for infection and what has been ruled out?
The woman, an AUT student and retail worker in her 20s, tested positive for Covid-19 yesterday. She works at A-Z Collections on High St.
She lives in Vincent Residences in Auckland's CBD, which is next door to the Grand Millenium managed isolation hotel.
On Monday evening, there was a fire alarm and residences of both the apartments and international returnees staying at the hotel mingled together on the street.
However, the Ministry of Health has said that this was unlikely to be the source of infection. The woman was already symptomatic earlier on Monday and may have been infected as early as Saturday - three days before the fire alarm.
Two Defence Force workers tested positive for the virus earlier this month, one of whom is a worker at Auckland's Jet Park quarantine facility.
One of these workers tested positive last Friday (November 6) and the other on Sunday. They had a meeting in Auckland last Wednesday, when they were likely to have been carrying the virus.
They NZDF workers went to a bar called Mezze for two hours last Thursday (November 7). The bar is on Durham St East in the CBD, which is about 100 metres from the new positive case's workplace, A-Z Collections.
As it stands, that is the closest geographical link between the November quarantine cluster and the woman. It is not known whether she was working or in the area when the Defence Force workers were at Mezze.
CCTV footage is being studied, but so far there is no evidence of any interaction between them.
In previous positive cases in New Zealand, transmission has occurred without close contact but through touching of infected surfaces.
In one case, a maintenance worker in Rydges hotel in central Auckland tested positive after touching a lift button pushed by a female traveller who later tested positive for Covid-19.
In another case, a returnee in an isolation facility in Christchurch was believed to have caught Covid-19 after touching a rubbish bin lid which had earlier been touched by an infected person.
One possible source of transmission could be if the Defence Force workers touched surfaces - a pedestrian crossing button or a door handle - in the CBD which were later touched by the woman, or another person who then passed it onto the woman.
It is not yet known how long Covid-19 can remain on surfaces. The World Health Organisation says its stability in the environment depends on several factors including relative temperature, humidity and surface type.
While we have not heard detailed results of the genomic testing, Hipkins' statement that the results are "incredibly encouraging" means that the strand of the virus detected in the Defence Force workers and the woman are likely to be very similar, and that the virus is unlikely to have passed through many people before it infected the woman.
As the virus is passed on from person to person over time, it mutates, and these changes can be detected during sequencing. The further it travels, the more it changes. If the genetic makeup of the woman's case was significantly different from the Defence Force cases, it could indicate that the virus has passed through many more people who have not yet been found.