Fears about silent spreaders of Covid — who suffer no symptoms but can pass the virus to others — may have been overblown.
A study of nearly 30,000 people has found asymptomatic carriers are about 68 per cent less likely to pass the virus on than those who get sick.
No10 used concerns about asymptomatic spread to justify forcing Britons to obey lockdowns and wear masks.
They were thought to account for up to a third of all infections and many scientists claimed asymptomatic patients were just as infectious as the sick.
Claims vs Reality
But a new global study spanning 42 countries, including the UK and US, found they were only responsible for as little as 14 per cent of cases.
They also estimate that their overall risk of passing the virus to someone else ‘about two-thirds lower’.
Scientists claimed Covid’s ability to spread asymptomatically was one of the reasons for harsh social curbs.
Experts analysed data from 130 studies from 42 countries.
They involved 28,426 people who caught Covid between April 2020 and July 2021.
Of these patients, nearly 12,000 had an asymptomatic infection, having tested positive on a PCR but having suffered no symptoms.
All of the studies included the results of community screening programmes, contact tracing, and investigations into specific outbreaks like on cruise ships.
They found the ‘secondary attack rate’, how likely people infected with Covid are to pass the virus to others, was 68 per cent lower for asymptomatic cases, compared to those with symptoms.
Scientists also estimated between 14-to-50 per cent of the Covid infections were asymptomatic.
But lead author, Diana Buitrago-Garcia, from the University of Bern in Switzerland, suggested their role in overall Covid transmission was minor.
If both the proportion and transmissibility of asymptomatic infection are relatively low, people with asymptomatic SARS-CoV-2 infection should account for a smaller proportion of overall transmission than presymptomatic individuals,’ she said.
Co-author, Professor Nicola Low, an expert in social and preventative medicine at Bern, said while it was clear asymptomatic cases were less infectious, the true scale of these cases in the pandemic was difficult to calculate.
‘The true proportion of SARS-CoV-2 infection is still not known, and it would be misleading to rely on a single number because the 130 studies that we reviewed were so different,’ she said.
‘People with truly asymptomatic infection are, however, less infectious than those with symptomatic infection.’
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