Trevor Bedford on Twitter: "Today, we're standing up a project called NextTrace that aims to enable digital participatory contact tracing and guide #COVID19 surveillance efforts. See a full description here https://t.co/0jKDupUlVb or get the summary in th

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epidemic is occurring because each infection results in 2 to 3 further infections. This process creates the exponential growth we have seen across countries, states, and cities. Any successful intervention must reduce this number of secondary transmissions. 2/20

Current broad-scale social distancing interventions aim to bring this number down by decreasing the number of contacts between people across the population. If people do not encounter each other, they cannot spread infection, regardless of whether they are infected or not. 3/20

Unfortunately, broad-scale social distancing is a blunt intervention with massive societal and economic costs. If we can move toward interventions targeted at infected and exposed individuals we can achieve the same outcomes with less societal hardship. 4/20

Contact tracing is a targeted intervention proven to reduce transmission and curb an infectious disease outbreak. By identifying possible exposures of an index case, the exposed individuals can be tested and isolated in the event that they are also infected. 5/20

Contact tracing targets surveillance resources and testing at individuals most likely to be positive, and also serves to test individuals early in the course of illness when isolation is most effective at reducing onward transmission. 6/20

However, traditional approaches to contact tracing do not scale; they rely on a huge investment in time and labor in which public health staff conduct exhaustive phone interviews to assess symptoms and exposure history among the network of persons under investigation. 7/20

Because of this, contact tracing is typically only conducted in the early “containment” phase of an epidemic when there are few enough cases that public health staff can keep up. 8/20

I believe, and others have proposed as well, that *digital participatory contact tracing* has the potential to substantially reduce transmission while avoiding the societal costs imposed by social distancing interventions. This will require: 9/20

Test: We will need to massively increase our testing capacity. This scale-up is now being tackled by a combination of state public health labs, hospital testing, and commercial laboratories. 10/20

However, relying on hierarchical reporting is fragile and may not result in timely distribution of results. We propose moving to a decentralized reporting system in which any lab performing diagnostic testing can broadcast test results in an anonymized fashion. 11/20

Trace: We propose a system in which, if an individual is confirmed to have COVID-19, they can register their case in an online platform. If they register, the platform will warn other individuals who were possibly exposed to this infection that they should seek testing. 12/20

The app / online platform would essentially conduct a coarse version of what epidemiologists do with interviews; it would build a contact history for the registered case, listing out contact events with other individuals that could potentially have resulted in transmission. 13/20

This system would use cell phone location and proximity data to detect possible exposure events while ensuring that privacy is preserved and data is secure. This obviously needs a great deal of attention to get right. 14/20

Guide: Beyond simply developing a system that can monitor individual-level interactions and exposure events, understanding high resolution transmission patterns on a broad scale would allow us to characterize the heterogeneity of the epidemic in different areas. 15/20

Variable levels of immunity, population densities, and age structures will create subtly different environments for transmission. Therefore, in addition to individual-level interventions, we will use this platform to help inform containment policies at the community level. 16/20