Australian health officials are scrambling to contact every Kiwi who's arrived in New South Wales in the past week-and-a-half, fearing they may have brought COVID-19 into the state with them.
NSW Health says 455 people who left New Zealand for Sydney since November 5 are being tracked down, after the emergence of a case of community transmission in Auckland this week.
It's been less than a month since the state opened the borders to Kiwis, who don't have to quarantine on arrival.
"All arrivals from New Zealand will be asked to monitor for even the mildest of symptoms and get tested and isolate if they appear unwell, then remain in isolation until a negative result is received, in line with routine advice for all people in NSW," NSW Health said in a statement.
They've been advised of the key locations linked to the latest case, such as where the case worked, the building they lived in and places they visited.
Advice was also given to Kiwis touching down in Sydney on Friday night.
"No passengers reported having attended the venues of concern and none had symptoms," NSW Health said.
"The risk posed by quarantine-free travel remains low. Airlines will ascertain if passengers have attended these venues before they leave New Zealand and if they have, they will be not allowed to travel."
The Auckland case was genomically linked to a known cluster on Friday afternoon, leaving the city at the lowest alert level. It's not known how she became infected, with no physical links yet discovered.
"We don't yet have a confirmed theory for how the virus was transmitted between the cases," COVID-19 Response Minister Chris Hipkins said on Friday.
No new cases have been picked up since she tested positive.
After experiencing a worrying second wave of cases in late July and early August, NSW managed to crush the curve. There has been only a single case of local transmission in the past week, after peaking at more than 400 a day. Fifty-three people have died of the disease in NSW to date, out of Australia's total of 907.
