The coronavirus is at its most infectious even before patients begin to show symptoms. This means by the time they are diagnosed they could have already infected many others.
According to Professor Christophe Fraser at the University of Oxford, about 50% of COVID-19 transmissions occur before the infected person develops any symptoms.
To prevent another wave of the pandemic as we come out of lockdown, healthcare authorities need to identify these people before they spread the disease and keep the virus in circulation.
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