For much of the past century, a strategy known as elimination was the gold standard for dealing with deadly new viruses.

But China’s abrupt reversal of its Covid Zero policy, which took it to an extreme, has cast doubts over the approach and left a gaping hole in the world’s game plan for the next pandemic. Even outside China, elimination measures such as stay-at-home orders proved politically unpopular and difficult to carry out.

With some medical experts doubting whether airborne respiratory pathogens can be suppressed, global public health officials are now without a consensus on how best to contain new infectious diseases. Early in the pandemic, proponents argued the strategy was morally, scientifically and economically superior to so-called mitigation approaches, such as slowing the spread of disease through physical distancing and limiting social gatherings or letting the virus loose among the young while protecting more vulnerable members of the population. As cases spread throughout the world, the full weight of the policy emerged, demanding strict border controls, lockdowns and extensive testing and contact-tracing.

But it also required fast action and global coordination, which was difficult to achieve. “In hindsight, people could have said let’s throw everything we can at this pandemic and try to stamp it out,” said epidemiologist Michael Baker, who was the architect of New Zealand’s early elimination Covid response.

“I think we had a reasonable chance of doing it.

But the opportunity is very early on in a pandemic.

Once there’s global distribution, you’ve got a huge challenge.” China’s experience, marked by months-long lockdowns, isolation and family separations, showed simultaneously that elimination was possible and that it came at a cost too high for most countries, especially democratic ones, to bear. The first example was in Wuhan, where Covid pervaded the city in late 2019 and was wiped out less than five months later.Proof of Concept “It was quite a revelation that China was able to stop transmission in 2020 in Wuhan,” said Baker, who recently became the director of the Public Health Communication Centre in New Zealand, a non-profit group designed to improve the way medical information and research is conveyed.

“That was the proof of concept.” New Zealand, which had a little more of a heads up, followed China’s example.

It halted the march of Covid with an intense, two-month stay-at-home order, plus other measures like contact tracing and quarantines.

A handful of other governments in Asia also pursued the policy, including in Hong Kong, Australia, Japan, Taiwan, and Singapore, with varying degrees of success.

Vietnam, Laos and Mongolia, with long borders and limited resources, also used it. The initial benefits were clear.

All were able to curb infections until pharmaceutical interventions like vaccines and antivirals were developed.

During that time, health care providers learned how to best treat patients, such as giving them steroids and positioning them on their stomachs, which boosted survival. Per-capita death rates in Covid Zero countries came in far below those that opted for mitigation, also known as flattening the curve.

While President Xi Jinping touted China’s success at saving lives, the unrelenting restrictions long after vaccines became widely available triggered protests while dragging on the economy.

Academics said the severity of China’s approach may have tainted the world’s perceptions of elimination measures which, when applied less harshly, have helped to contain deadly diseases like polio, measles and SARS. “It created a false alternative in which a draconian, individual rights-destroying lockdown was seen as one option, and the other was to do nothing,” said Amesh Adalja, a senior scholar at Johns Hopkins Center for Health Security. China imposed a tracking system that forced millions of people to routinely get laboratory-run PCR tests to do things like go to the office, eat in a restaurant or ride the subway.

Simply being in the proximity of someone who later tested positive could mean lead to home confinement or being taken to a quarantine camp. In Shanghai, 25 million people were locked down for two months in 2022.

In other cities, workers fled manufacturing plants that used closed-loop systems that kept them inside the factories.

Residents scaled fences and shoppers rushed exits when rumors of infections cropped up, for fear of being forced into weeks of isolation.

Protests, once unheard of, erupted. In the face of such discontent, China abruptly dropped its stringent elimination measures in December. China wasn’t alone in grappling with the costs of elimination.

Thousands of Australians caught outside the country when Covid flared were denied re-entry for more than 18 months, while Melbourne endured six lockdowns over 262 days in a bid to keep the virus out.

New Zealand’s “Go Hard, Go Early” approach was also criticized when tough lockdown steps led to rising unemployment and domestic violence.

Both countries have since seen a change in leadership.Public Revolt Even governments that decided against elimination, opting instead to flatten the curve, struggled to persuade people to follow basic control methods.

In the US and many parts of Europe, topics like mask-wearing and immunizations for high-risk people became political quagmires, despite studies showing they slowed infections and saved lives. It was particularly difficult to persuade people to accept sacrifices like online schooling and social isolation without knowing how long the pandemic would last.

Especially in the early stages, health officials were unsure which mitigation measures would prove successful or how long it would take to develop pharmaceutical interventions. “We were hoping we could switch this thing off,” with immunity from vaccination or previous infection preventing transmission of the virus, said Jodie McVernon, director of epidemiology at the University of Melbourne’s Doherty Institute.

“Those hopes were relatively short lived.

We moved on from the idea that we can immunize the world and turn the infection off.” The nature of Covid, with its mutations and hyper-infectivity, made elimination particularly challenging. “When you are dealing with omicron, there is no threading the needle,” McVernon said.

“Once omicron was out of the bottle, there was no squeezing the genie back in.” A unified global response is now even less likely in the next pandemic.

The number of emerging infectious diseases continues to grow due to global warming and the development of rural areas that are home to wild animals, which act as hosts for many viruses. Countries that were able to initially follow an elimination strategy are likely to pursue it again, while those that couldn’t are unlikely to be swayed by the example set during Covid, said Chen Xi, an associate professor specializing in aging and public health at Yale University in Connecticut. “It all comes down to a country’s culture and political governance structure,” he said.