Need to focus on silent transmission of Covid-19, say experts

Expert says these cases must be detected and isolated to control the outbreak of pandemic

By Author  |  Published: 8th Jul 2020  12:30 amUpdated: 8th Jul 2020  12:48 am
silent transmission
SAFETY FIRST: People are wearing protective gear like face masks, overcoats to fight the spread of coronavirus. — Photo Anand Dharmana

Hyderabad: Researchers, epidemiologists and experts are increasingly pointing towards silent transmission of SARS-CoV-2 as a major factor, if not addressed quickly would lead to a prolonged fight to contain the spread of the Covid-19 infections, not only in the States but across the Country.

At present, the ongoing response to Covid-19 pandemic in almost all the Indian States including Telangana is to focus on symptom-based isolation of positive patients. And yet, the cases of Covid-19 have continued to surge not only here but in the entire country, which is a clear indication that public health experts might be overlooking silent transmission of SARS-CoV-2 from pre-symptomatic and asymptomatic cases.

Pre-symptomatic cases are those persons who are Covid-19 positive but are yet to develop symptoms while asymptomatic cases are those cases that are positive but will not have the typical Covid-19 symptoms at all.

Professor of Molecular Medicine and founder of Scripps Research Institute, United States, Dr Eric Topol recently highlighted a US-based study titled ‘The Implications of silent transmission for the control of Covid-19 outbreaks’, which was published on July 6 in the peer-reviewed journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).

“Majority of Covid-19 infections are attributable to silent transmission from a combination of pre-symptomatic and asymptomatic infections. To control outbreaks, the silent infections must be detected and isolated,” Dr Eric Topol on Twitter said.

In fact, a few days later, Chief Scientist of World Health Organisation (WHO), Dr Soumya Swaminathan took to the social media platform and referred to the same PNAS study and said “Pre-symptomatic patients can transmit Covid-19, highlighting the importance of surveillance and isolation of symptomatic cases and quarantining of close contacts”.

The study found that ‘the majority of incidences of Covid-19 infections may be attributable to silent transmission’ from a combination of pre-symptomatic stage and asymptomatic infections. Consequently, even if all the symptomatic cases are isolated, outbreak may nonetheless unfold, the study said.

Researchers said that silent disease transmission during the pre-symptomatic and asymptomatic stages are responsible for more than 50 per cent of the overall attack rate in Covid-19 outbreaks.

“Furthermore, such silent transmission alone can sustain outbreaks even if all symptomatic cases are immediately isolated. The results corroborate recent contact tracing studies indicating a substantial role of pre-symptomatic transmission among 243 Covid-19 cases in Singapore and 468 Covid-19 cases in China,” the study said.

 silent transmission

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