This paper examines the impact of diagnostic efficiency on the COVID-19 pandemic. Using an exogenous policy on diagnostic confirmation, we show that a one- day decrease in the time taken to confirm the first case in a city publicly led to 9.4% and 12.7% reductions in COVID-19 prevalence and mortality over the subsequent six months, respectively. The impact is larger for cities that are farther from the COVID-19 epicenter, are exposed to less migration, and have more responsive public health systems. Social distancing and a less burdened health system are likely the underlying mechanisms, while the latter also explains the more profound impact on reducing deaths than reducing infections.
Act Early to Prevent Infections and Save Lives: Causal Impact of Diagnostic Efficiency on the Covid-19 Pandemic