Coronavirus: New Zealand's new COVID-19 outbreak 'detected later than it could've been' - expert

Public health experts say the current Auckland infections were picked up too late, and want mandatory daily saliva tests for all frontline border workers. 

They also believe there's a likely reason transmission occurred in the first place - and it may not be because of virus transfer via airline laundry. 

LSG Sky Chefs is the workplace of one of the three infected. Her job was washing linen and blankets from incoming international flights.

However the laundry's unlikely to be the source, according to Professor Nick Wilson, a Professor of Public Health at Otago University.

"From what we know scientifically, it is extremely remote given that no one has shown any evidence from around the world that there's transmission between a surface or object to infect a person," he said.

The most likely scenario is person to person contact - for example, that the worker got the virus from another person, possibly an airport worker or air crew employee.

There is another possibility. If the woman's child got the virus first, there could be undetected community spread. 

"The child and the mother developed symptoms at a similar time so that is a possibility - that there is another chain of transmission in the community," said Prof Wilson.

Under Government rules, LSG says its laundry employees were not subjected to mandatory fortnightly tests as they don't work at the airport.

However, as a precaution, the company did ask laundry staff to be tested every two weeks. But LSG says it just reminded employees of this, and didn't confirm whether tests were actually being done, saying employees health data is personal information.

Professor Philip Hill, the founding director of the Centre for International Health at the University of Otago, says this outbreak was "probably detected later than it could have been".

Part of the reason for that is the testing regime - it isn't frequent enough, he says.

In September last year, he was one of the authors of a testing report that warned "all efforts should be made to introduce saliva testing as soon as possible".

"I think we've been slow to get our saliva testing going," he said.

"When we were doing the interviews for that report, it was clear talking to people in Hong Kong for example that they'd been doing routine saliva testing for four months already."

On January 25, saliva testing was introduced, but only on a voluntary basis at high-risk quarantine hotels. 

It was then temporarily put on hold due to testing demand following the infection-control failures at the Pullman. 

Prof Nick Wilson says we should "move very quickly" to daily saliva testing for all managed isolation and quarantine staff and border workers. 

There have also been calls to reduce the numbers arriving here - a suggestion not accepted by the Prime Minister.  

"All of New Zealand has an obligation, a legal obligation, to allow citizens to return to their home country," said Jacinda Ardern.

However Prof Wilson believes "turning down the tap" is a realistic option.

"Legal scholars have identified ways we can definitely slow the number of arrivals," he said.

He thinks it's time to focus only on humanitarian cases, and limit the risk until the vaccination programme begins.

Professor Hill says while it's early days in this outbreak, we should have confidence that the Auckland public health unit is in a better position to contact trace than it was during the August outbreak.