Covid-19

We’re going into lockdown. Here’s why

Analysis: New Zealand is going into lockdown in order to prevent tens of thousands of deaths. Marc Daalder reports.

In 48 hours, New Zealand is going into lockdown. All bars, restaurants, cafes, cinemas, museums, libraries and playgrounds will shutter, or at least cease any activities that require face-to-face interaction.

Most workplaces will be shut. Tens of thousands of people may have no jobs to do, as they are unable to perform their duties remotely.

All of this is happening despite the fact that we have just 102 cases of Covid-19 and all but two of them can be traced to overseas travel or other confirmed cases. Why?

It could save tens of thousands of lives. Here's how:

Suppression needed, overseas figures show

Overseas estimates in a paper from the Imperial College London found that taking no action to fight the virus could leave 250,000 dead in the United Kingdom and 2.2 million in the United States. Taking "mitigation" measures - known cases self-isolate, as do their families and all people over 70 self-quarantine - would only halve the death toll. But "suppression" measures, which would involve reducing physical contact to the bare minimum, working from home and closing schools, can cut the toll by 90 percent.

As this Newsroom analysis shows, these suppression measures would have to be in place more or less constantly until a vaccine is ready - approximately 18 months away. They could be relaxed slightly when cases dropped for a short period of time - roughly two months on lockdown, one month off - but this would have to be carefully monitored to avoid an outbreak that would overwhelm the health system and spiral out of control.

These estimates, when presented to UK and American officials, helped change government policy there. In New Zealand, as Newsroom reported, the same figures have been very influential in resetting the Government's strategy towards Covid-19.

Now we too want to suppress any community transmission. After that, we'll ideally be able to ease our measures, keep our borders largely closed and coast the rest of the way until a vaccine is developed.

What would it look like here?

The modelling for New Zealand is just as stark. Figures based on the Imperial College London paper and released this morning by the University of Otago show that 100,000 New Zealanders would be killed if no action was taken and 90 percent of the population was infected.

"In the worst-case scenario, the models are starkly clear: up to 90 percent of the population could end up getting infected and up to 100,000 people in New Zealand could die. Our health system would not be able to cope with demand and lots of people would not get the treatment they needed," University of Canterbury Professor Michael Plank, who helped with the University of Otago's modelling, told the Otago Daily Times.

In her address to the nation, Ardern said projections she had seen were equally compelling. "If community transmission takes off in New Zealand, the number of cases will double every five days. If that happens unchecked, our health system will be inundated, and tens of thousands New Zealanders will die," she said.

"Everything you will all give up for the next few weeks, all of the lost contact with others, all of the isolation, and difficult time entertaining children – it will literally save lives. Thousands of lives.

"The worst case scenario is simply intolerable. It would represent the greatest loss of New Zealanders’ lives in our country’s history. I will not take that chance."

Transmission is here

The Government announced the lockdown just an hour after the Ministry of Health confirmed two cases of Covid-19 would now be treated as community transmission. That means we don't know where the people got it or who they got it from.

This transmission could be very limited - maybe two or three degrees of separation, with few or no other people infected along the way. It could also be more widespread. Perhaps there are a dozen or more people unknowingly carrying it and unknowingly infecting others.

"That tells us there's been some uncontained spread and, based on what we know from overseas, that's likely to be growing exponentially," University of Auckland Professor Shaun Hendy told Newsroom.

Fear of hidden community transmission is what motivated University of Otago Department of Public Health Professor Michael Baker to call for a lockdown last week.

Lockdown gives breathing room

A lockdown now will ensure that carriers, whether they know they have Covid-19 or not, infect far fewer people. On average, Hendy said, a person with Covid-19 will infect 2.5 other people. If that number can be reduced to below one, then the numbers of infected will start to dwindle instead of rise.

By keeping people away from one another and ensuring that those with the virus can only plausibly infect their families or housemates, New Zealand is seeking to reduce that infection rate. This also makes it much easier to trace who an infected person came in contact with - you don't have to track down every attendee at a global cattle conference but instead just have to test each person in a single home.

When community transmission of Covid-19 takes hold, the number of cases doubles every five days. By locking down the country early and reducing the infection rate to below one, the number of times cases double - and the speed at which they do so - can be steeply cut.

In fact, Plank's estimate shows deaths could be cut to 6500 even if community transmission is widespread. If not, the total number of cases could even be limited to hardly more than the 102 we currently have.

"The best-case scenario, which we still have a shot at, is to stamp the virus out before it really takes off and stop new cases from coming in from overseas," Plank told the Otago Daily Times. "If we can do this we could get away with only a few hundred cases. This is going to be a long game though – realistically it’s likely to be 12-18 months before a vaccine or treatment is available."

Tests also needed

The lockdown also gives the country's labs time to scale up their testing. Labs have been running more than a thousand Covid-19 tests a day over the past few days, but experts say they are running out of supplies and the workforce can't continue at this pace. At the same time, the backlog of tests is significant - Newsroom understands that some tests taken Thursday morning have yet to be reported.

In comment provided through the Science Media Centre on Saturday, University of Otago Associate Professor James Ussher, Labtests director Gary McAuliffe and Canterbury DHB Dr Joshua Freeman said "diagnostic labs are really struggling to maintain testing capacity due to supply chain issues, which will be ongoing, as they are worldwide".

"The influx of test requests outside the current case definition is currently threatening to overwhelm our capacity to test at all. The Ministry of Health is doing the best it can under the circumstances, but the testing labs are in crisis," they said.

What's next?

The hope is that community transmission is limited so far. However, even if it is more widespread, the lockdown will help New Zealand cope with the crisis.

With more tests, easier contact tracing and reduced contact between people, community transmission can be quashed or contained. Eventually, it could be eliminated.

After that, Hendy said, we can start to look at lifting some of the restrictions. Parts of the country could move to alert level three or two in four weeks' time, when the Government reevaluates the lockdown. This is particularly likely for the South Island, where there are not yet any reports of community transmission.

"If we slow the spread down now, then we've got a chance of containing. That means that perhaps - and we'll see this, potentially, in a couple of weeks to a month - the Government will start to think this has been successful and they'll start to think about relaxing those restrictions," Hendy said.

Given time, the lockdown could be lifted nationwide. If strict border measures remain in place, life could return to alert level two or even one, where people wash their hands a bit more and keep their distance from strangers but otherwise enjoy life.

"We simply weren't as prepared as some of the countries that got SARS," Hendy said. "They were able to take a different strategy. They've been able to do things like keep schools open with rigorous testing. We'd like to manoeuver ourselves into a position where we can do that. By slowing things down now, we've got a chance to get ourselves into the same position as the countries that dealt with SARS and appear to be coping well with the current outbreak."

If testing develops to the point where accurate tests can return results in a matter of hours, Hendy said, the border restrictions could also be relaxed. Either way, however, some semblance of control and care around Covid-19 will be required for many months to come - at least until we have a vaccine.

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