Covid 19 coronavirus: Chief science adviser: How and when we exit alert level four

By RNZ

New Zealand has settled on an elimination strategy to stamp out Covid-19. The Prime Minister's chief science adviser Juliet Gerrard says if you're an epidemiologist, the strict definition of elimination is to rid the country or an area of the virus, except for a small number of manageable cases.

The devil is in the detail, Gerrard told Nine to Noon's Kathryn Ryan.

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"The strategy that New Zealand's using to enact this elimination pathway is to keep it out at the border and stamp it out when it gets here."

However, we have to expect that we might get outbreaks, she said.

"Before we drop levels, we have to be absolutely sure that if we've missed some cases, and the outbreak does pop up, that we flatten that small curve."

To assume there will be no leakage would be foolish because Covid-19 is such a challenging disease to get on top of, she said.

"The cases we've seen so far are consistent with the imported cases, rather than an enormous amount of local transmission and so I think we can all be encouraged."

However, now is not the time to relax.

"We need everyone to keep doing their bit, stay home, wash their hands, don't leave their bubble to really make sure that every pocket of transmission that we've got are contained and are stamped out before we leave lockdown."

Over the next two weeks, the Ministry of Health needs to go out and hunt cases in low-case areas, she said.

"All the experts agree that an enormous contract tracing capacity is probably the number one priority for living safety at level 3 and level 2.

"If the worst happened and we did have an outbreak, we would need to be able to trace all the contacts of up to 1000 cases."

Gerrard said there are two type of data that can speed up contact tracing.

Aggregated data, like that released by Google, already shows that we've made progress, she said.

The other type, personal data, has been used by countries which have been successful in their response to Covid-19 because they don't worry about privacy issues as much as we do in New Zealand, she said.

"There's no off-the-shelf solution that you can just buy and bring in to New Zealand, you have to adapt it to New Zealand's situation and by that I mean the data management system, and there we've got an advantage because everyone's got an individual NHS number."

The technology to contract trace efficiently is being worked on, and privacy and security issues worked through, Gerrard said.

She said with the large number of people coming home to New Zealand from overseas, it's hard to think we could be in a better place by this point.

"Everyone's fingers are crossed that the levelling off and possible dropping down holds and that will be a sign of success."

• Covid19.govt.nz: The Government's official Covid-19 advisory website

However, it's only now that we will begin to see the effects of lockdown because of the lag between being exposed to the virus and getting symptoms, she said.

"The next few days should be a real test of whether what we've done is working successfully enough to get us out of lockdown at the end of the month."