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(B A Raju/TOI, BCCL, Chennai)

Turns out that fears about asymptomatic COVID spread were overblown. A novel study has claimed that people infected with SARS-CoV-2 but had no symptoms are two-thirds less likely to pass virus to others.

Asymptomatic people were feared to be silent spreaders of COVID-19 pandemic, which has so far claimed six million lives, and almost 15 million excess mortality.

But a review of 130 different studies published in the open-access journal PLOS Medicine found that the proportion of asymptomatic infection was 50 per cent or lower in most studies.

The studies published through July 2021 showed that most SARS-CoV-2 infections were not persistently asymptomatic, and asymptomatic infections were less infectious than symptomatic infections.

“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 pre-symptomatic individuals,” Diana Buitrago-Garcia of the University of Bern, Switzerland and her team wrote in the paper.

The team included 130 studies, with data on 28,426 people with SARS-CoV-2 across 42 countries, including 11,923 people defined as having asymptomatic infection. An estimated 14-50 per cent of infections were asymptomatic.

The results showed that the secondary attack rate was about two-thirds lower in people without symptoms than in those with symptoms.

“The true proportion of asymptomatic 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. People with truly asymptomatic infection are, however, less infectious than those with symptomatic infection,” said co-author Nicola Low from the varsity.

However, the team also cautioned that “when SARS-CoV-2 community transmission levels are high, physical distancing measures and mask-wearing need to be sustained to prevent transmission from close contact with people with asymptomatic and pre-symptomatic infection.”


The above article has been published from a wire agency with minimal modifications to the headline and text.