Abstract
The impact of the extent of testing infectious individuals on suppression of COVID-19 is illustrated from the early stages of outbreaks in Germany, the Hubei province of China, Italy, Spain and the UK. The predicted percentage of untested infected individuals depends on the specific outbreak but we found that they typically represent 60–80% of all infected individuals during the early stages of the outbreaks. We propose that reducing the underlying transmission from untested cases is crucial to suppress the virus. This can be achieved through enhanced testing in combination with social distancing and other interventions that reduce transmission such as wearing face masks. Once transmission from silent carriers is kept under control by these means, the virus could have been fully suppressed through fast isolation and contact tracing of tested cases.
Highlights
The impact of the extent of testing infectious individuals on suppression of COVID-19 is illustrated from the early stages of outbreaks in Germany, the Hubei province of China, Italy, Spain and the United Kingdom (UK)
Such asymptomatic individuals can act as silent carriers for SARS-CoV-2 and have been suggested as a key factor promoting the rapid spread of the virus[16], similar to what has previously been observed with other infectious diseases[17]
We did not find detailed data on daily tests performed in China but according to the COVID-19 Government Response Tracker[44,45], testing and contact tracing have remained at high levels in China since the early stages of the epidemic
Summary
The impact of the extent of testing infectious individuals on suppression of COVID-19 is illustrated from the early stages of outbreaks in Germany, the Hubei province of China, Italy, Spain and the UK. Studies testing for SARS-CoV-2 infection in both symptomatic and asymptomatic individuals[10,11,12], suggest that reported asymptomatic carriers can represent 50% or more of the cases at the time of testing These may include true asymptomatic that remain asymptomatic throughout their infection and pre-symptomatic individuals that become symptomatic after testing. Most countries test individuals when they have symptoms, and unreported infections are likely to include most of the asymptomatic individuals and a fraction of those with symptoms Such asymptomatic individuals can act as silent carriers for SARS-CoV-2 and have been suggested as a key factor promoting the rapid spread of the virus[16], similar to what has previously been observed with other infectious diseases[17]. If recovery from infection leads to immunity, one Scientific Reports | (2021) 11:20728
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