“There are a lot of uncertainties. Now the question is, 'where did they get the transmission? Who else is there?'” he told SBS News.
“This offers the system a window to efficiently launch a search for the source of infection. This is not at all an overreaction, it is planned for three days, but if they don’t know the source they may extend it, or if there are new cases,” he added.
All four of the cases are from the same family, and dozens of other family members and close contacts have been sent into isolation.
One of the family members is believed to have travelled elsewhere on the north island of New Zealand before testing positive.
University of Auckland Associate Professor Siouxsie Wiles said some of the family's close contacts are already reporting symptoms and she expected the number of cases to rise.
She said while the source of the infection isn’t known it is likely to be from contact with someone associated with the border, rather than from asymptomatic carriers who have been in the community all this time.
New Zealand officials are investigating the possibility that its first COVID-19 cases in more than three months were imported by freight
“There is someone associated with the borders or isolation quarantine who has passed it on to someone who has passed it on to them, most likely,” Dr Wiles said.
The outbreak was not a sign that the elimination strategy was impossible to maintain, Dr Wiles added.
“No this is not a sign that elimination hasn’t worked. The border is the place we expect it to come in, letting anybody into the country is how you can let it happen, we are still on our elimination track so we have to work very hard and very fast to contain this outbreak,” she said.
“There has been a plan on how to rapidly scale up testing and contract tracing and that everything is going to plan. Though I imagine we will be in restrictions for a bit longer than Friday."
University of Otago rural health expert Garry Nixon said the most important thing now that Auckland had been placed on a higher alert level was limiting movement between areas.
“Because of this differential approach of different alert levels in different parts of the country, it means we are going to have to be particularly careful about movements between the areas,” he told SBS News.
“The last thing we want is the virus to get out of Auckland and into parts of the country where there is freer movement and it is more likely for the virus to spread,” he added.
New Zealand authorities on Wednesday also announced a woman in her 50s, who arrived in New Zealand on 7 August, had tested positive for coronavirus.
Four additional “probable” cases are awaiting test results, the country’s top health official Ashley Bloomfield said.
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If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080.
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