Spillover effect

Experts said that as Shanghai is a major transportation hub, COVID-19 cases in the city may spill over to other parts of the country. As a result, it is crucial to uphold dynamic clearance and for the outbreak to be brought under control as soon as possible to reduce its impact.

Shanghai has one of China's most developed and interconnected public transportation systems. As of the end of 2020, the city operated 1,585 public transportation routes with a total length of 9,116 kilometers, according to the Information Office of Shanghai Municipality.

Moreover, Shanghai has 14 municipal highways and seven national expressways connecting to other big cities, including Beijing, Xi'an, capital of Shaanxi province, and Kunming, the Yunnan provincial capital. Shanghai also has 67 roads leading to the neighboring provinces of Jiangsu and Zhejiang.

Shanghai Pudong International Airport is one of the busiest in China. In 2019, it handled more than 76 million travelers, 511,840 flights and over 3.6 million metric tons of cargo.

Xu, from Shanghai Jiao Tong University, said that if the city cannot achieve dynamic clearance of cases, the virus may spill over through human transmission or through goods to other parts of the Yangtze River Delta region and even the entire country.

"This may have a growing negative impact on China's social and economic development. In the short run, life and the economy in Shanghai will be affected by the quarantine measures, but taking the nation as a whole, containing the spread of the virus within a specific region will ensure the rest of the country maintains normal operation," he said.

"Therefore, Shanghai must uphold the dynamic zero-COVID policy. This is a sound strategy that will ensure the stability and growth of the region and the nation," he added.

Wu Huanyu, deputy director of the Shanghai Municipal Center for Disease Control and Prevention, said in an article posted by the city's information office there would be unimaginable consequences if Shanghai did not abide by the dynamic clearance policy.

If the number of infections continued to rise rapidly, the virus could mutate into something more serious, which is a risk that the city could not take, Wu added.