When historians assess how countries approached the coronavirus pandemic, New Zealand is sure to stand out.

The South Pacific nation is alone among its western peers in explicitly attempting to eradicate the virus. It adopted one of the strictest lockdowns in the world before a single death was reported, and has isolated infections to keep the disease from spreading out of control.

The early signs are promising. The rate of new infections has dwindled to the lowest in weeks, and the death toll -- at 11 -- is one of the lowest among developed nations. The prime minister, Jacinda Ardern, decided on Monday to start easing some quarantine measures that requires everyone but essential workers to stay at home.

“We have the opportunity to do something no other country has achieved -- elimination of the virus,” Ardern told reporters last Thursday in Wellington, as she cautioned against relaxing restrictions too quickly.

The island nation’s lofty goal of elimination is not without critics, who say it’s unrealistic and comes at a devastating economic cost. Even if New Zealand succeeds, its borders will have to remain closed to much of the world for a considerable period to keep the virus out. That will decimate the tourism industry, its largest source of foreign exchange earnings.

Central to New Zealand’s approach is a scientific fact that most western leaders appear to have ignored, according to Michael Baker, a professor at the University of Otago’s Department of Public Health in Wellington who sits on the government’s Covid-19 Technical Advisory Group. That is that the virus usually has an incubation period of five to six days, twice as long as influenza.

“That means that when someone gets sick, if you isolate them quickly and round up their contacts, you can quarantine those people and interrupt that chain of transmission,” said Baker. “With influenza you can’t really do that because by the time you’ve found their contacts it’s too late, they’ve infected other people.”

And yet most countries treated Covid-19 as if it were influenza, he said, trying to slow its advance rather than eradicate it. Nations including the U.K. and the U.S. opted for such mitigation and suppression efforts after they found themselves overwhelmed by cases.

Changing Tactics

New Zealand’s initial response took that approach too. In the early stages of the outbreak, Ardern spoke of “flattening the curve” of the virus’s spread to ensure the health system could cope.

That all changed on March 23, when she announced a four-week nationwide lockdown would commence two days later, saying modeling showed that without the measures “tens of thousands of New Zealanders could die.”

Industries were shuttered, schools were closed, and the only shops allowed to stay open were supermarkets, some corner stores and pharmacies. At that stage, New Zealand had only 102 cases and no deaths. Most countries resorted to such measures only after fatalities soared. When the U.K. announced its lockdown, also on March 23, it had 6,650 Covid-19 cases and 335 people had already died.

Exit Strategy

The theory is that imposing tough restrictions early halts the spread of the pathogen and eventually allows an exit strategy to crystallize. The economic hit may be worse upfront, but activity can resume sooner. The alternatives of mitigation or suppression may require restrictions to stay in place for many months, prolonging the economic pain.

New Zealand’s strategy, which requires extensive testing and contact-tracing capabilities, is supported by the statistics. While total cases have risen to 1,409, it has avoided the exponential growth seen in Europe and the U.S. Just eight new infections were reported last Friday, the lowest number in four weeks.

The island nation, with 5 million residents, has a similar population to Ireland, which has seen more than 13,000 infections and almost 500 deaths. And while New Zealand’s 11 fatalities compare with 10 in Singapore, that Southeast Asian country is now struggling with a wave of infections from dormitories housing low-wage foreign workers.

A comparison with neighboring Australia is more complicated. Australia has far more cases, at 6,468, and deaths have climbed to 63. But the infection rate comes out to 254 per million people, less than New Zealand’s 292 per million.

Australia’s Approach

Australia’s results have come despite less stringent restrictions. It has allowed more industries to continue operating, such as construction, and consumers can still get a haircut or buy a takeaway meal, keeping many workers on lower incomes employed.

“Australia is doing better than New Zealand without going to that extreme,” said Peter Collignon, an infectious diseases physician at Canberra Hospital who advises the Australian government.

Collignon questions whether New Zealand’s eradication strategy is realistic.

“The reality is this virus is everywhere, it’s all around the world,” he said. “So even if you’re successful for a short period of time, how long do you do this for? Six months? Two years? Invariably, you’re going to get the virus re-introduced.”

One concern is the phenomenon of asymptomatic transmission. The possibility that people can pass along the disease even though they show no symptoms underscores the challenge of containing the pandemic.

‘Nirvana’ Scenario

Brendan Murphy, Australia’s chief medical officer, told a New Zealand parliamentary committee April 14 that eradicating the virus is a “nirvana” scenario.

“We are pursuing a very aggressive suppression strategy,” he said. “Obviously we would like to achieve elimination (but) we’re pretty doubtful that could be maintained for the long-term given the incredible border measures you would need to have.”

For Baker, there are benefits in trying to eliminate the virus, as well as evidence it can be done -- China, for example, appears to have succeeded in stopping the Wuhan epidemic and preventing wider transmission within its borders.

He believes more countries, including Australia, could yet adopt elimination strategies and eventually form an “eastern hemisphere bloc” with nations like China, Singapore and South Korea within which travel will be possible.

“Maybe it’s a bit optimistic, but at least we have an exit strategy and a plan,” Baker said. “That seems a lot more appealing than the mess that Europe and North America are going to be in for the foreseeable future.”