Contact tracing can be effective in curbing COVID-19 pandemic only if testing is fast: Lancet study

Contact tracing can be effective in curbing COVID-19 pandemic only if testing is fast: Lancet study
Speed of contact tracing strategies is essential to slow coronavirus transmission.

Reducing the time between the onset of symptoms and receiving the test result is important for improving contact tracing effectiveness, say experts.

Written by Longjam Dineshwori |Updated : July 19, 2020 1:00 PM IST

Contact tracing is considered as the best tool to contain the coronavirus (COVID-19) pandemic until there's a vaccine. It is the process of identification of persons who may have come into contact with an infected person. Health experts believe that contact tracing will break the chains of transmission of infectious disease and thus help in controlling infectious disease outbreaks. But the speed of contact tracing strategies is essential to slow coronavirus transmission, suggested a study, adding that the delays in testing will significantly hamper this process.

In case of COVID-19 testing is delayed by three days or more after a person develops symptoms, even the most efficient contact tracing strategy cannot reduce onward transmission of the virus, said authors of the study, published in The Lancet Public Health journal.

"This study reinforces findings from other modelling studies, showing that contact tracing can be an effective intervention to prevent the spread of the SARS-CoV-2 virus, but only if the proportion of contacts traced is high and the process is fast," IANS quoted study author Mirjam Kretzschmar from the University of Utrecht in the Netherlands as saying.

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Key to the success of contact tracing

Improving access to Covid-19 testing along with the use of digital that minimises tracing delays is crucial for the success of a contact tracing approach, the researchers noted. For example, they said that mobile apps can help speed up the process of tracking down people who are potentially infected.

According to them, contact tracing can successfully help in controlling the infectious disease outbreak if a country can keep the rate of transmission of the virus, known as the Reproduction or R number, below one. This means the number of individuals who will be infected by a single infected person must be limited to less than one.

For the study, the researchers used a mathematical model that assumes that around 40 per cent of virus transmission occurs before a person develops symptoms. The model predicted that if applied in the right way, contact tracing could reduce the number of people a person with COVID-19 passes the virus on to from 1.2 to 0.8.

This can be achieved if at least 80 per cent of people who are eligible are tested and there are no delays in testing after the onset of symptoms. In addition, at least 80 per cent of contacts must be identified on the same day as the test results are received, the model predicted.

The researchers noted that conventional contact tracing takes a minimum of three days and is less efficient at tracking down contacts compared to mobile app technologies, which are instantaneous.

Overall, the study concluded that reducing the time between a person developing symptoms and receiving a test result is important for improving contact tracing effectiveness.

Aarogya Setu is the world's most downloaded contact-tracing app

According to recent research by Sensor Tower Store Intelligence, India's Aarogya Setu has seen 127.6 million downloads since its launch on April 2. This number is more than any other contact tracing app in the world, it stated. Turkey's Hayat Eve S ar app and Germany's Corona-Warn-App are other top contact tracing apps with 11.1 million downloads and 10.4 million downloads respectively.

The analysis looked at the adoption rate of government-endorsed contact tracing apps in the world's 13 most populous countries. The countries included Australia, France, Germany, India, Indonesia, Italy, Japan, Peru, The Philippines, Saudi Arabia, Thailand, Turkey, and Vietnam.

A total of 173 million people from these 13 countries were estimated to have downloaded various contact tracing apps since March 2020.

With inputs from IANS