The Auckland mother who tested positive for COVID-19 was not included in the group of border workers required to undergo fortnightly testing as she was considered to be at a lower risk of contracting the virus, says Director-General of Health, Dr Ashley Bloomfield.
Health officials are now considering whether the pool of border workers required to undertake mandatory testing should be widened.
The mother, Case A, is the first of three new community cases detected over the weekend. Case B is her child, a student at Papatoetoe High School, and Case C is the father.
Under the COVID-19 Public Health Response (Air Border) Order, a specific group of 'high risk' border workers are required to undergo mandatory testing every 14 days to ensure they have not contracted the virus from international aircrew, new arrivals or transit passengers.
Case A, an employee at the Auckland Airport branch of LSG Sky Chefs - a flight catering facility - worked in the laundry department and was therefore not considered to be at a high risk of contracting the virus, Dr Bloomfield said.
Yet on Saturday night, health officials were alerted that the woman had tested positive - and exactly how she became infected remains a mystery.
Speaking to The AM Show on Tuesday, Dr Bloomfield confirmed that the woman was not included in the current Border Order and was therefore under no obligation to undergo a test every 14 days.
It follows speculation that the woman had missed a scheduled fortnightly test after the Ministry of Health revealed she was last swabbed on January 18 - a swab that returned a negative result.
"There was no requirement for her to be tested every two weeks," Dr Bloomfield said. "I'm not sure she necessarily can be judged to have 'missed a test' because she and her colleagues were not required to be part of the testing programme."
He reiterated that the woman does not have contact with international arrivals, aircrew or airside border workers in her role.
"The reason she's not captured in the current order is that she's quite arms-length from international travellers, from anyone working airside, and aircrew," he said.
Dr Bloomfield added that LSG Sky Chefs is still encouraging employees outside of the mandatory testing programme to get swabbed frequently as part of the company's broader health and safety measures.
"There are some employees there that are required to be tested, [but] the employer was offering and providing testing to the wider workforce as part of their health and safety response."
The woman's infection has signalled to health officials that a review of the current testing order is needed, Dr Bloomfield said.
The assessment will determine whether the current pool of border workers required to undergo mandatory testing should be expanded, and whether the frequency of testing should also be increased.
"What we're doing now is looking again at the current testing order - who is required to be tested and the frequency of testing.
"It may well be we need more frequent testing of some people and widen the number of people being tested."
By the end of Monday, seven of the woman's nine close workplace contacts had returned negative results, Dr Bloomfield confirmed.
It was also confirmed on Tuesday morning that another close contact of the family - from the 42 identified - had tested negative.
Two work-related contacts of the father, Case C, have also returned negative results. All 42 close contacts remain in isolation and will be re-tested in case of possible incubation.
The source of the community cases remains unknown, although Prime Minister Jacinda Ardern has speculated that a transit passenger or surface transmission could be possible explanations.
Genome sequencing conducted on Sunday evening could not find a direct match between the case and another infection in New Zealand's database. However, a closer inspection is underway with a particular focus on cases of the UK variant B.1.1.7 - the same strain the three family members are carrying - from the last month or two.
ESR is also analysing the global database to see if there is a potential match between the case and a transit passenger or an aircrew worker.