NZ's responses to Covid-19 and polio vastly different

New Zealand has adopted the right approach to Covid-19 - despite trade and travel continuing during the waves of polio that hit the country in the 20th century, epidemiologist Michael Baker says.

Prof Baker told Sunday Morning that in the face of the Covid-19 coronavirus, countries weigh up the options available to them at the time.

He responded to questions sent in from listeners, including one who pointed out the country did not shut down on any of the occasions when polio threatened the health of many. Polio was eliminated in 1977 as a result of vaccination.

Baker, who is an epidemiologist, said polio was a virus that caused huge concern for the country and school closures were common to dampen down transmission.

The main thing with handling Covid-19 is to think of the alternative - what the country is doing is expensive and disruptive but what other choice did it have. By choosing elimination New Zealand would join other countries such as Taiwan and Australia in being largely free of the virus.

If we chose mitigation, as is the approach in Europe, the virus would continue to circulate. Everyone he had spoken to internationally said they would love to have elimination as an option.

"At the moment if you're sitting in Europe you don't have those choices ... all you've got is varying degrees of suppressing transmission."

The "slow-burn approach" is emerging in countries like Portugal where they are doing quite well in dampening down transmission but they are faced with having to deal with suppression once they come out of lockdown.

Other countries such as Sweden are taking a lighter approach to controlling the spread of the virus so they have higher numbers of cases. He said it would only be in the future that it will become more obvious which option is the best strategy.

So far as treatments are concerned, in China scientists are taking blood samples from people who have recovered from Covid-19 and producing a form of anti-viral serum using the antibodies as a building block to treat new cases. It's a different approach, Baker said.

"This is using convalescent plasma treatment. This is really at the moment I think the only therapy that is looking very effective and this is because you are using the antibodies of those recovered patients to treat a viral infection in someone who is very ill and so this is quite a promising approach and I'm sure there will be pharmaceutical companies looking at how this can be applied more widely."

The best aspect of the move to alert level 3 at 11.59pm tomorrow is getting people back to work and having the chance to support the likes of local restaurants.

There was no change to the rules around physical distancing and accepting that what we touch in public places may be contaminated.

He urged people to hold off on social celebrations for another month at least. "We know from the modelling work you need about eight weeks for a chance to get on top of this virus."

Surveillance data is providing a lot of data that we don't have community transmission.

"Most worrying will be if we suddenly saw spontaneous cases just popping up around the country that we couldn't explain. That would indicate widespread community transmission but I think that's most unlikely the way things are going."

It would be vital to stick with physical distancing in alert level 3 to avoid this, Baker said.

Read more about the Covid-19 coronavirus:

• See all RNZ Covid-19 news
• Your Covid-19 questions answered - from health and employment to managing anxiety
• A timeline: How the coronavirus started, spread and stalled life in New Zealand
• Covid-19 symptoms: What they are and how they make you feel
• Scientific hand-washing advice to avoid infection
• Coronavirus: A glossary of terms
• The Coronavirus Podcast