Given the control measures already in place and the willingness most people have shown to comply with restrictions, we believe New Zealand can get back to its elimination status.

But we suggest a number of additional measures to speed up progress, including an update of the current alert system to make the use of masks mandatory in indoor public spaces and to place tighter controls on venues with a high transmission risk, including bars, gyms, choirs and churches.

Getting the outbreak back under control

The use of masks should be mandatory for all indoor public places at level 2 (which is currently in place across New Zealand) and this requirement should be added to a revised alert level system. The effectiveness of simple reusable fabric masks can approach that of standard surgical masks.

We should also update advice on venues with a particularly high risk of transmission, including bars, nightclubs, gyms and choirs and church gatherings (anywhere people sing). Some of these places have been implicated in large outbreaks.

One Japanese study noted many COVID-19 clusters were associated with: "heavy breathing in close proximity, such as singing at karaoke parties, cheering at clubs, having conversations in bars, and exercising in gymnasiums."

Similarly, there are studies on outbreaks associated with dance classes and a choir practice. The closure of such places could be built into alert level 2 - or perhaps a distinct alert level 1B where all other places remain open.

Even at higher alert levels, we should reassess school closures to reflect more nuanced evidence about risks and benefits at different ages. The aim should be to keep younger children in school wherever possible.

The information about physical distancing at schools on the Ministry of Education website is now outdated and needs revision. In particular, mask use should be universally adopted by secondary school-aged children, bringing them into line with recommendations for adults to prevent viral spread.

The new outbreak affects several work places in Auckland and better sick leave provisions are in discussion to ensure workers with mild illnesses and those waiting for test results don't come to work. This support is particularly important for workers at the highest risk of infection: border workers, air crew and staff at managed isolation and quarantine facilities.

Further economic support packages will be necessary for people unable to work under level 3 restrictions.

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Effective measures are already in place

The government's rapid implementation of strong control measures is appropriate. This decisive approach allowed New Zealand to eliminate COVID-19 back in May. The country is now better prepared than earlier in the year in a number of ways because:

• we know that it is possible to eliminate the virus and there are inspiring examples from other jurisdictions (including Taiwan, most Australian states and territories, and Fiji)
• we have the logistics in place to carry out mass testing in the community
• the manual contact tracing system has improved, including better integration of regional public health units into a single national system
• we have genomic sequencing methods available to help identify the source of the outbreak
• and the Ministry of Health has adopted World Health Organization advice on the use of face masks.

All these measures, together with alert level 3 restrictions in the greater Auckland region, will help bring the outbreak under control. There is only a small risk these measures could fail and force New Zealand (or some regions of the country) to repeat a level 4 lockdown.

Necessary measures for the longer term

It is almost certain the current outbreak is due to a border-related event. This was the source of the large outbreak currently affecting the Australian state of Victoria and spilling over into New South Wales.

Previous modelling work shows it can take several weeks for a case to be detected following a biosecurity breach. It has been suggested the virus may have entered New Zealand on refrigerated freight, but this source is much less likely than a failure with the quarantine system.

Given this outbreak, a thorough review of border and quarantine systems, including ports, is now necessary. After some concerning quarantine breaches, we now have a more robust system of border controls, including stricter testing regimes in managed isolation and quarantine facilities.

But further improvements will be needed, and this could include more regular testing of border and quarantine staff and the use of digital technologies to ensure staff keep appropriate distance from people in quarantine and to track their movements when off-duty (within privacy safeguards).

Improvements in contact tracing are ongoing. A CovidCard device is currently going through a trial in Rotorua, but the government should explore alternatives such as smartphone apps using the Apple/Google platform, as used in Ireland and Spain.

Phone data were used successfully in South Korea and New Zealand should evaluate this option, within appropriate privacy safeguards.

Finally, we need an update on the scope for COVID-19 surveillance through testing of wastewater. Several cities, including Paris, are exploring this. In New Zealand, researchers have detected the virus in wastewater, and this form of early detection of outbreaks would reduce the need for routine community testing.