Explainer: Why are Shanghai's COVID infections nearly all asymptomatic?

Article reports that epidemiologists examining the biggest Chinese outbreak of COVID-19 in two years are trying to ascertain why the proportion of asymptomatic cases is so high, and what it could mean for China's future containment strategy. The number of new confirmed community transmitted cases in the major financial hub of Shanghai reached 4,477 on Tuesday, a record high, but only 2.1% showed symptoms. The share of symptomatic cases over the previous seven days was around 1.6%. Although outbreaks overseas have demonstrated that Omicron was less deadly than its predecessors, with lower levels of hospitalisation, the rate of symptomatic infection was relatively high compared to China's numbers.