For more than a year, Chinese officials have beat back the coronavirus with a tried formula: Strict lockdowns at the sites of outbreaks. Lengthy quarantines for travelers. And citywide testing when new cases appear.
But an outbreak of the fast-spreading Delta variant could challenge China’s zero-tolerance approach toward new infections.
In the outbreak, centered in the eastern city of Nanjing, about 200 cases have been reported as of Friday. But infections have spread rapidly, with patients emerging in at least six Chinese provinces and the capital, Beijing, in just three weeks.
As officials move to contain the spread, the highly infectious Delta variant could prove to be a more difficult foe than the original version of the virus, which China stamped out with harsh efficiency in 2020. With most of China’s people already vaccinated, the emergence of Delta could also present a test for the country’s domestically made vaccines and could force the authorities to take even tougher steps to control the virus.
Chinese officials say they have administered enough vaccine doses to cover around 800 million people. But several other countries that used Chinese-made vaccines have reported that fully inoculated people continue to be infected, although most do not appear to become seriously ill. Data also indicates that the Delta variant is more easily transmitted, even by those who have had two doses of more effective vaccines, such as those produced by the companies Pfizer and Moderna.
The outbreak in China began when a group of airport workers in Nanjing were sickened around July 10, probably from exposure to an infected person who arrived on a flight from Russia, according to city officials. Two rounds of citywide testing of more than eight million people turned up 184 cases.
To stop the spread, Nanjing has increasingly shut down services, first closing the airport, then restricting indoor gatherings. This week, the city authorities closed parts of the expressway that connects Nanjing with other major cities in Jiangsu Province.
As handfuls of cases connected to Nanjing have popped up in other provinces, the authorities there have moved swiftly to impose restrictions.
In the central city of Zhangjiajie, in Hunan Province, indoor public areas including movie theaters and malls were closed after the authorities said that four people with the virus, all asymptomatic, went to a show in the city. Nearly 200 miles away in the provincial capital of Changsha, the authorities banned indoor gatherings in response to one confirmed case.
In central Sichuan Province, where seven cases were found, the authorities declared parts of the capital, Chengdu, a medium-risk zone. The discovery of three cases in the northern city of Shenyang prompted officials there to begin tracking visitors who had come from other areas with outbreaks.
Perhaps most worrying to officials are two cases that appeared in Beijing, where the government has generally followed stricter prevention policies. Officials said that a husband and wife who traveled from Zhangjiajie had tested positive and that 654 people who had been in close contact with them had been placed in quarantine.
Li You contributed research.