Symptomatic patients more infectious: Study

NEW DELHI: A person who has symptoms of coronavirus disease (Covid-19) is four times more likely to pass the virus on to others than someone who remained asymptomatic, and the highest risk of infection comes from sharing a home with an infected individual, according to a statistical analysis of dozens of contact-tracing reports, which offers new evidence to underscore the need for people to isolate themselves as soon as they develop signs they may be ill.

The researchers from Imperial College London also found that households have the highest transmission rates among indoor settings when compared to being in a workplace and casual social spaces, with the chance of one family member infecting another becoming significantly higher if the duration of exposure is more than 5 days.

“This analysis provides some of the first evidence that asymptomatic infections are substantially less infectious than symptomatic cases. It also reinforces growing evidence of the importance of household transmission, especially in the context where symptomatic cases are not isolated outside the home,” said Imperial College professor Neil Ferguson, whose modelling in March led the UK to announce a lockdown to stop transmission.

The study was based on a meta-analysis from 45 contacttracing studies from around the world published till mid-July.

“Understanding the conditions where transmission is more likely to occur is essential in guiding policy interventions to reduce transmission...” said Imperial College researcher Andria Mousa.

This analysis provides some of the first evidence that asymptomatic infections are substantially less infectious than symptomatic cases. NEIL FERGUSON,

Professor, Imperial College London