China’s recent outbreak of the highly contagious Delta variant is prompting mass testing and causing leaders to review restrictions as they look to contain the deadly virus.

China, which is dealing with over 300 new cases in more than two dozen cities, has 144 different medium and high-risk areas -- the most since the initial outbreak in early 2020. The country has reported 4,636 deaths in 93,000 confirmed cases.

Since the outbreak, China has adopted a “zero tolerance” policy and quarantined every case in order to prevent new infections from abroad as well as further outbreaks. The actions by the Chinese government had an impact on the daily work and life of millions of people and demonstrated that government officials needed to get the virus under control without shutting the country down.

On Monday, seven infections were reported in Wuhan, and 20 were reported on Wednesday, including 8 asymptomatic cases, according to the Hubei provincial health commission. The city of 11 million people was placed on a 76-day lockdown in January of 2020 and it proved to be a success. The surging Delta variant is putting officials on high alert and some fear yet another strict lockdown. During Wuhan’s initial lockdown, millions of citizens had to stay home and rely on officials and volunteers to provide for their daily needs.

The ongoing outbreak began in Nanjing, Jiangsu province, in eastern China. It was linked to a Russian plane that arrived at Nanjing Lukou International Airport on July 10.

“It is believed that the cleaners did not follow strict anti-epidemic guidelines after cleaning Flight CA910 and contracted the virus as a result. The infection spread further to colleagues, who are responsible for cleaning and transporting garbage on both international and domestic flights,” reported state news agency Xinhua.

The virus has spread to 26 cities but not all infections have been linked to Nanjing. On Monday, 63 cases and 50 asymptomatic cases were reported in Zhengzhou, with most cases being linked to an outbreak at a hospital. Outbreaks like this prompted the Chinese government to impose nationwide travel restrictions.

Dr. Zhang Wenhong suggested his country’s containment strategy could change.

“We will definitely learn more from the ongoing outbreak,” Zhang said, calling it a stress test for the nation.

China will need to step up its vaccination process and treat those who are infected while letting everyday life and business travel run normally.

“I don’t think ‘zero tolerance’ can be sustained,” said Xi Chen, a health economist at Yale School of Public Health.

China’s handling of the virus will be tested when the Winter Olympics arrive in Beijing in February of 2022. China shut down much of the world’s second-largest economy in 2020.