Study Says Asymptomatic People Not Responsible for Spreading Covid as Thought

COVID-19 patients with no symptoms are two-thirds less likely to pass the virus to others. But a review of 130 different studies, published in the open access journal PLOS Medicine, found that the proportion of asymptomatic infection was 50% 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% of infections were asymptomatic.

Asymptomatic COVID Cases

The results showed that the secondary attack rate - a measure of the risk of transmission of SARS-CoV-2 - 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.

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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."

Source-IANS