China's Covid zero target gets more elusive as asymptomatic cases increase

China reported more infections in people who exhibited no symptoms of Covid-19 on Tuesday than in those who were actively suffering from the virus, indicating the challenge it faces in eliminating the highly infectious and insidious pathogen.

Among the 89 people who learned they were harboring the virus, 46 had no outward signs of disease. It is the first time those with covert infections outnumbered those with symptoms during the broadest outbreak that China has experienced since the virus first emerged in Wuhan in late 2019. 

Of the 31 provinces on the Chinese mainland, 20 have reported infections caused by the delta variant, including the capital Beijing.

China remains the only country in the world bent on weeding out every infection within its borders, defying a global trend of learning to live with Covid after more infectious variants rendered restrictions less effective and made eliminating it markedly more difficult. Mass vaccination and the rollout of booster shots have significantly reduced the burden of the disease, with the majority of fully vaccinated people developing mild or no symptoms if they contract a breakthrough infection.

“It’s different now than a year ago because the consequences of infection, particularly if you’re vaccinated, are less marked than they were a year ago,” said Peter Collignon, an infectious disease physician and professor at the Australian National University Medical School in Canberra.

While China has seen severe disease among elderly patients with underlying medical conditions, the country hasn’t reported a single death related to Covid for nearly 10 months. With more than 75% of the population fully vaccinated, most patients experience only mild symptoms. The country has reported at least a dozen asymptomatic infections every day for the past week. 

Many of the stealthy infections were found only after authorities were alerted to the potential for community transmission following a case that emerged during routine testing of workers and residents. In some extreme cases, close contacts tested positive after they emerged from prolonged quarantine periods.

“The reality is that it’s more difficult to control now,” Collignon said. “But equally, the consequences -- providing you get high levels of vaccination -- are much, much less than they were a year ago.”