Covid-19: New Zealand yet to define elimination despite officials' comments

9:12 am on 28 April 2020

New Zealand has been making international headlines overnight after the prime minister talked about "eliminating" Covid-19.

Photo: RNZ /Dom Thomas

The BBC's website led with a story titled Coronavirus currently eliminated in NZ, while the Daily Mail had a story headlined New Zealand has 'achieved elimination' of coronavirus and CNN had New Zealand claims 'elimination' of coronavirus with new cases in single digits.

Most stories quoted Director-General of Health Dr Ashley Bloomfield from yesterday's briefing, where he said that there was only one case in the whole of April that hasn't had its origin successfully traced.

But University of Otago public health expert Michael Baker told Morning Report New Zealand was yet to create a formal definition of what elimination of Covid-19 is.

"I think the concern is that as we reduce that distancing, particularly as we head to level 2, that's when any remaining chains of transmission might suddenly appear, and overseas we have seen unfortunately outbreaks of this virus at that point.

Professor Michael Baker, a public health medicine specialist at the University of Otago

Photo: University of Otago

"So it might be that a definition of elimination requires that you see no evidence of transmission say at level 2 or level 1, that's where I think if the virus was present we would see it returning."

Despite that, Prof Baker said the country was headed in the right direction and the statements from officials did not suggest a declaration of elimination at this point.

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Prime Minister Jacinda Ardern, who yesterday said the virus was "currently" eliminated, told Morning Report it was not unreasonable to use the term elimination - but that meant "zero tolerance for cases".

"In technical terms the place where we are now, that would not be an unreasonable use of the word elimination," Ardern said.

"There is genuine consensus that what we need to do is make sure we have the same level of success we've seen at level 4," she said.

"No-one here is sitting on their laurels, no-one is saying job done, no-one is saying final success.

"I would urge no New Zealander to be complacent."

Ardern said she did not believe she had talked of elimination too early.

"We can say with confidence that we do not have community transmission in New Zealand. The trick now is to maintain that."

"When I talk about elimination it does not mean zero cases, it means zero tolerance for cases," she said. "The idea of Covid being completely gone, that is eradication - so there are important differences there."

Elimination would also not be lost because of an occasional case appearing that was managed via border restrictions, or even because of a short chain of transmission, Prof Baker said.

A disease could still be eliminated if there was the ability to stamp it out quickly, he said.

"But a definition of elimination, for example, wouldn't allow for occasional cases to pop up in the community unexpectedly, because that would suggest ongoing community transmission.

"What we can't tolerate is cases of community transmission in New Zealand, particularly if we don't know where they come from… I would say we can't have community transmission if we have elimination."

The definition would not just need to rely on academia, he said, but would also need to cover a range of situations and be widely discussed to be robust and possibly compatible with Australia.

"I think both Australia and New Zealand will have to put a lot of effort into saying what is the definition of elimination, at what point would we allow travellers to go backwards and forwards between our countries."

Prof Baker said the level 3 period would be a good opportunity to work on the definition of elimination.