Why are most of the new cases in China asymptomatic?

Epidemiologists are studying the current outbreak in China to try to determine why the proportion of asymptomatic cases is so high and what it might mean for China’s future containment strategies.

China’s financial hub reported a record 4,477 new local coronavirus cases in the past day, but only 2.1 percent (96 cases) showed symptoms, the Shanghai health Commission said on Tuesday. In the past seven days, about 1.6 percent of cases had symptoms.

While outbreaks elsewhere in the world have shown that Omicron has been less deadly than previous strains and has caused fewer hospitalizations, the rate of symptomatic infections is higher than the Chinese figures.

The proportion of asymptomatic omicron infections in the UK is estimated to be between 25% and 54%, according to government data.

While the UK and other countries have implemented the “live with the virus” policy and lifted all COVID-19 quarantine restrictions, the Chinese government is still sticking to its dynamic zero-out policy, and international travel is still severely restricted.

Why is the proportion of asymptomatic infected persons in Shanghai and Even China so high? Here are some explanations.Large-scale rigorous testing

China is the only major country in the world to conduct large-scale, untargeted tests that are bound to find more asymptomatic infections and, as expected, potentially more symptomatic cases.

Lower vaccination rates with higher toxicity

The low pathogenicity of Omicron itself, combined with China’s relatively high vaccination rates, may have reduced the number of symptomatic infections.

The infection was detected early

Asymptomatic more, and early screening, the early discovery has a relationship. Extensive screening has allowed many patients to be detected and isolated in the early stages of infection without showing symptoms. An asymptomatic infected person today may become a mild or moderate case tomorrow or the day after.