With a new community case in Auckland - a woman in her 20s - the best-case scenario is for a potential source to be identified which points to the border or to a known case.
The worst-case scenario is that it remains unknown and her circle of contacts is so wide that there'll be no choice but to put Auckland back into level 3 lockdown lite.
That's because, without a source, there could be umpteen branches of transmission already spreading throughout the city, and even throughout the country with the level 1 freedoms we've been enjoying.
That's why the Government put Auckland into lockdown lite and the rest of the country into level 2 in August when four community cases came to light. The source has never been identified, with the earliest symptoms from a cluster case 12 days before the first cases were detected.
That was enough time for the outbreak to spread far and wide, including on public transport and via church services, across the city and into the Waikato, eventually infecting 179 people.
Prime Minister Jacinda Ardern's Cabinet paper on the Government's "rapid response plan" suggests an immediate move to lockdown while the new case is interviewed.
The crucial question is whether there is serious risk of ongoing undetected transmission, with key elements being the number of contacts, the person's movement - especially if it includes regions outside Auckland - and whether there is a known source.
"The interview would cover a range of factors including whether the case has a clear connection to the border, the case history including symptom onset and severity, and the individual's movement patterns," Ardern says in the Cabinet paper.
"At this point I anticipate encouraging only essential travel for people in the affected
region ... We may also implement immediate temporary (eg around four days) local or
regional controls, including restrictions on movement (particularly between regions),
requiring people to stay at home and limiting gathering sizes.
"These actions would reduce the risk of further transmission while we are learning more about the movements of the cases and any contacts."
This is exactly what happened in August.
Asked why Auckland hasn't already moved alert levels, Covid-19 Response Minister Chris Hipkins said that Cabinet had more time - and more information - before publicly revealing the August cases.
But it was indicative that he effectively asked Aucklanders to move to level 2 immediately by keeping physically distant, and by wearing masks on public transport and on flights in and out of Auckland.
Ardern's paper outlines possible scenarios - following a few days of information gathering - and what to do about them:
• One or two further cases detected among close contacts with a known source at the border - move the region to alert level 2 (physical distancing, restrictions on gatherings), though level 1 with "some specific controls" may be appropriate.
• A single cluster of connected cases in the region with no evidence of
wider community transmission - move the region to at least level 2, likely level 3, while keeping the rest of the country at level 1.
• Widespread community transmission in the region but no cases in other regions - move the region to level 3 or even level 4, while moving the rest of the country to level 2
• At least one cluster in the region and confirmed cases in other regions - move affected regions to level 3 and unaffected regions to level 2.
Health chief Ashley Bloomfield said the case hadn't been to the supermarket, lived alone, and had not had a roaring social calendar since first feeling ill on Monday.
But she went to work while feeling ill, and it's been almost a week while she was potentially infectious before she moved into quarantine.
With luck, a clear sign to a known case or to the border will emerge, with no movement outside Auckland and a small ring of contacts identified.
If not, and if the Government continues the precautionary approach that has served it so well so far, Auckland is staring down the barrel of at least a move to level 2.
And probably level 3 until we know more.
What is alert level 3?
There is a high risk the disease is not contained.
• Multiple cases of community transmission occurring.
• Multiple active clusters in multiple regions.
Range of measures that can be applied locally or nationally:
• People instructed to stay home in their bubble other than for essential personal movement — including to go to work, school if they have to, or for local recreation.
• Physical distancing of 2 metres outside home, or 1 metre in controlled environments like schools and workplaces.
• People must stay within their immediate household bubble, but can expand this to connect with close family/whānau, or bring in caregivers, or support isolated people. This extended bubble should remain exclusive.
• Schools (years 1 to 10) and Early Childhood Education centres can safely open, but will have limited capacity. Children should learn at home if possible.
• People must work from home unless that is not possible.
• Businesses cannot offer services that involve close personal contact, unless it is a supermarket, pharmacy, petrol station or hardware store providing goods to trade customers, or it is an emergency or critical situation.
• Other businesses can open premises, but cannot physically interact with customers.
• Low risk local recreation activities are allowed.
• Public venues are closed. For example, libraries, museums, cinemas, food courts, gyms, pools, playgrounds, markets.
• Gatherings of up to 10 people are allowed but only for wedding services, funerals and tangihanga. Physical distancing and public health measures legally must be maintained.
• Healthcare services use virtual, non-contact consultations where possible.
• Inter-regional travel is highly limited. For example, for critical workers, with limited exemptions for others.
• People at high risk of severe illness, such as older people and those with existing medical conditions, are encouraged to stay at home where possible, and take additional precautions when leaving home. They may choose to work.