80% of initially asymptomatic cases develop Covid-19 symptoms later: Study

Prashasti Awasthi Mumbai | Updated on September 26, 2020 Published on September 26, 2020

According to a new study published in the journal PLOS Medicine, true asymptomatic cases of the novel coronavirus comprise a minority of infections.

The researchers at the University of Bern, Switzerland, and colleagues, maintained that the world is yet to know the full spectrum of the coronavirus and how it gets transmitted.

Authors mentioned in their study that some Covid-19 positive people may experience severe infections that can even lead to viral pneumonia, respiratory distress syndrome, and death. While others demonstrate no symptoms at all and remain completely asymptomatic or have nonspecific symptoms.

The researchers conducted the study to better understand the proportion of asymptomatic people with SARS-CoV-2 who never show any symptoms and the proportion of people who are asymptomatic at the time of diagnosis but develop symptoms later.

For the study, the researchers reviewed the literature of 79 studies that reported empirical data on 6,616 people, 1,287 of whom were defined as asymptomatic.


The researchers estimated that 20 per cent of infections remained asymptomatic during follow-up. The limitation of the study was that it could not ascertain the cases of false negatives among asymptomatic cases.

The researchers noted that accurate estimations of both cases are important to better understand the distribution of the virus

Researchers revealed that around 80 per cent of asymptomatic cases eventually develop the symptoms of the virus. This means that presymptomatic transmission may significantly contribute to overall SARS CoV-2 epidemics.

Diana Buitrago-Garcia at the University of Bern said in a statement cited in PLOS: “The findings of this systematic review of publications early in the pandemic suggests that most SARS-CoV-2 infections are not asymptomatic throughout the course of infection.”

“The contribution of presymptomatic and asymptomatic infections to overall SARS-CoV-2 transmission means that combination prevention measures, with enhanced hand and respiratory hygiene, testing and tracing, and isolation strategies and social distancing, will continue to be needed,” Buitrago-Garcia added.

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Published on September 26, 2020
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