PM explains science for 4-week lockdown

Prime Minister Jacinda Ardern says there is no plan for New Zealand to lift the alert level four lockdown early – and there is science informing that decision.

Because of the time lag it took for Covid-19 to rear its head, four weeks was the minimum time needed to ensure the chain of transmission was stopped, she said.

The virus could take up to 14 days to show signs, so cases being seen now could have had the virus prior to the lockdown, but were then asymptomatic.

The lockdown ought to have stopped wider transmission but those people may have passed the virus to close contacts before level four was put in place.

‘‘So we can expect to see these close contacts coming through now and next week as well. And of course those people could have passed it onto others in their bubble or their essential workplace as well.’’

Health officials needed to better understand the cases of community transmission and have certainty there was not a wider presence in the community than what was already known – especially in areas with low case numbers – before lockdown could lift, she said.

‘‘Absence of evidence is not evidence of absence. We need to be absolutely sure we are not missing a silent outbreak.’’

That was why surveillance testing would be so important and this would get under way soon, Ardern said.

This would be a version of sentinel surveillance such as that used to ascertain how the flu spreads.

It would be undertaken in regions where there was no ‘‘rich

data’’ because there had not been many cases or much testing, she said.

Last week health officials did not rule out going door to door in communities.

Significantly better data, about the risk of unseen transmission, would be collected during the next two and a half weeks, she said, and this would help inform decision-making about moving out of level four with confidence.

A broad set of indicators would be used to assess movement between various levels, Ardern said.

This included ensuring community spread was under control, so the sacrifices made by New Zealanders will have paid off.

Actions during the reminder of level four would be about doubling down to ensure the gains made in the first half were not squandered in the second, she said.

All actions taken during level four were about minimising the amount of time New Zealand had to stay in lockdown, in order to stamp out the virus, she said.

‘‘Let me be really clear, I don’t want New Zealand to be at level four a minute longer than needed, but equally there is no plan to move from level four early.’’

The Government was determined to make sure it stamped out Covid-19, she said.

That means broader testing and in particular surveillance testing, more and faster contact tracing and strong enforcement of the lockdown rules and border controls.

‘‘Now is not the time to ease up, but rather the time for all of us to focus even harder on the mission we have.’’

The Government was planning to implement mandatory quarantine at the border and this would likely happen during the last two weeks of level four.