The Omicron-fueled increase in the country’s COVID case numbers is testing China’s zero-COVID policy, which aims to quickly squash any outbreak through strict safety measures and immediate lockdowns.

China has pointed to the measures as a success in curbing the pandemic—as the government reported no COVID deaths from January 2021 until March 19 of this year. But the current surge in cases is putting strain on its economy, as the more mild and transmissible Omicron variant threatens widespread closures in some provinces.

Despite economic concerns, officials in China are standing by the zero-COVID policy, pointing to the country’s relatively low number of cases amid the outbreak as proof that the approach continues to work.

Liang Wannian, head of China’s National Health Commission COVID-19 response expert panel, defended the policy during an appearance on China Central Television that was reported on by Hong Kong newspaper the South China Morning Post.

“The dynamic zero-Covid approach means we need to swiftly identify the outbreaks and cut the transmission chain to go towards the direction of zero Covid, or the transmission will be continuous and connected, causing a large-scale rebounding of cases,” Laing said.

Liang also acknowledged the Omicron variant means China “can’t achieve” its goal of having zero COVID-19 patients in society but insisted the approach continues to prevent the number of cases from being even higher, the South China Morning Post reported.

“China has seen many sporadic cases, or even clusters, but the rising momentum is not exponential, which is exactly because we have taken a series of strong interventional measures to curb the momentum,” Liang said.

Wu Zunyou, an epidemiologist for the Chinese Center for Disease Control and Prevention, also doubled down on the policy, telling the Chinese state-run newspaper Global Times: “COVID-19 won’t disappear in the short term and our fight [against COVID-19] will be a long-term battle.”

On Monday, Shenzhen, a key manufacturing hub, reopened after its citizens completed three rounds of COVID-19 testing, Reuters reported. The temporary shutdown forced some major companies, including Toyota and Apple, to temporarily halt operations, which raised concerns about the global supply chain.

An outbreak in Tangshan, an important city for the steel industry that is home to more than seven million people, was reported on Saturday, prompting the government to order mass testing and traffic controls, according to the South China Morning Post. Financial hub Shanghai is also grappling with a surge in cases, forcing Shanghai Disney resort to temporarily shut down on Monday.

“Due to the current pandemic situation, Shanghai Disney Resort, including Shanghai Disneyland, Disneytown and Wishing Star Park will be temporarily closed from Monday, March 21, 2022,” a message on the resort’s website said. “We will continue to monitor the pandemic situation and consult local authorities, and will notify guests as soon as we have a confirmed date to resume operations.”

The surge in cases has also brought new deaths. China confirmed the first two deaths in more than one year last week in the region of Jilin, a hotspot of the recent COVID wave that has also reported thousands of new cases in recent days. Both of the people who died were elderly patients with underlying conditions, according to the Associated Press. Only one victim had been vaccinated.

China reported only two deaths during 2021, but experts have raised questions about the validity of that claim. Since the beginning of the pandemic, China has faced questions about whether or not officials are undercounting the number of cases and deaths.

Cases in China peaked earlier in March—with 77,285 new cases being reported on March 3, the highest number since the start of the pandemic—but cases still remain high, according to data from Johns Hopkins University.

China also has a high vaccination rate, with nearly 89 percent of its population fully vaccinated, according to data from Johns Hopkins.