E-Paper
Exposure to coronavirus needs to be digitally traced
In the model, the scientists assume that the threshold for stopping the spread of the epidemic is to reduce the reproduction number (R) – the number of people one patient can infect – to below one.
The spread of the coronavirus disease (Covid) is too rapid to be contained by the traditional manual contact tracing of infected people, a new study has concluded, calling for digital and phone-based methods to control the contagion at scale.
The study, conducted by professors at the University of Oxford and published in the journal Science, also flagged significant concerns around privacy and ethics and urged governments to be transparent and constitute an independent board to oversee the use of such invasive techniques.
“Our analysis suggests that almost half of coronavirus transmissions occur in the very early phase of infection, before symptoms appear, so we need a fast and effective mobile app for alerting people who have been exposed. Our mathematical modelling suggests that traditional public health contact tracing methods are too slow to keep up with this virus,” said Christophe Fraser of Oxford University’s Big Data Institute, Nuffield Department of Medicine, and one of the authors of the study.
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The paper has been published at a time when India is experiencing a surge in infections – the number has almost tripled in five days – and governments have pressed the local police, district administrations and even anti-terror squads to trace people who attended or have come into contact with those who attended an Islamic congregation in March in New Delhi’s Nizamuddin, which has emerged as the biggest hotspot of Covid-19 in the country.
The government has linked at least 647 cases of the infection to the congregation, attended by delegates from overseas and all over India.
In the study, scientists use a mathematical model of infectiousness through four routes of transmission: symptomatic (known contact with someone exhibiting Covid-19 symptoms), pre-symptomatic (contact with someone before symptoms showed up), asymptomatic (direct transmission from individuals who never experienced symptoms), and environmental (when direct close contact is not known).
In the model, the scientists assume that the threshold for stopping the spread of the epidemic is to reduce the reproduction number (R) – the number of people one patient can infect – to below one. This would mean that each Covid-19 patient would infect less than one person, and the disease would eventually die out. The model of infection spread is assumed to be exponential – as has been witnessed in several countries.
The scientists found that instantaneous contact tracing significantly improved the chances of containing the epidemic and reducing R to below 1, while a delay of three days – typically associated with manual contact tracing – led to the probability nearing zero. To be sure, this assumed that no other parameters – such as weather or medical intervention – were involved in the situation.
“At the current stage of the epidemic, contact tracing can no longer be performed effectively by public health officials in the UK, and many countries across Europe, as coronavirus is spreading too rapidly. Our research of early data from other countries shows that patient histories are incomplete - we don’t know the details of the person we sat next to on the bus,” said David Bonsall from Oxford’s Nuffield Department of Medicine and one of the study’s authors.
The scientists suggested the use of a mobile phone app that keeps a temporary record of proximity between individuals so that it can immediately alert close contacts of diagnosed cases and prompt them to self-isolate. The paper also proposed an algorithm by which instantaneous signals, carrying details of proximity and location, are transmitted to and from a central server, which also receives coronavirus diagnoses.
This enables recommendation of risk-stratified quarantine and physical distancing measures in those known to be possible contacts – similar to the measures undertaken by South Korea after a 61-year-old woman attended a church congregation and ended up infecting close to 5,000 people.
“To work, this approach needs to be integrated into a national programme, not taken on by independent app developers. If we can securely deploy this technology, the more people that opt-in, the faster the epidemic will stop, and the more lives can be saved,” Bonsall said.
But the paper flags significant ethical and privacy concerns and stresses the need to avoid coercive surveillance. It calls for oversight by an independent advisory board, a transparent algorithm, data protection and sharing of knowledge.
“People should be democratically entitled to decide whether to adopt this platform. The intention is not to impose the technology as a permanent change to society, but we believe under these pandemic circumstances it is necessary and justified to protect public health,” the study said.
