Contact tracing is a laborious process that is used to identify and reach out to people how have had contact with someone with a confirmed case of an infectious disease. As part of an effort to contain an outbreak, those contacts are isolated or quarantined. If the contacts develop into confirmed cases, then contact tracing is performed on their contacts too.
I’d like to clarify some terms to put things into perspective. An outbreak is when an infectious disease occurs in unexpectedly high numbers but is limited to one geographic area. When the infection spreads to multiple areas, it is called an epidemic. When the infection spans multiple countries or continents, it is called a pandemic.
Contact tracing is a containment strategy for a disease outbreak. When an infectious disease becomes an epidemic or pandemic, contact tracing is not feasible, and we switch to mitigation strategies such as school closures, limiting restaurants to take-out or delivery, and other social distancing measures. The United States is predominantly addressing COVID-19 through mitigation strategies. However, if we get the disease sufficiently under control and can begin to relax social distancing measures, we will need to ramp up contact tracing to focus once again on containment.
The Margolis Center for Health Policy at Duke University released guidance on a COVID-19 containment strategy that addresses testing, surveillance, contact tracing, isolation, and quarantine. As described in this NPR article, contact tracing is a resource-heavy and time-consuming process.
It was announced today that Apple and Google are working together on a contact tracing infrastructure using smartphones. Here are identical press releases from Apple and Google. More information is available via both technical documentation and a layperson illustration.
The first phase of the collaboration will include APIs that will enable data sharing across Apple’s iOS and Google’s Android devices. This would allow app developers to implement the APIs and share data between the apps and health authorities. The second phase will include a Bluetooth-based contact tracing platform that, according to The Verge, would detect signals from nearby phones at 5-minute intervals and store those connections but not their physical locations. If one person develops COVID-19, it would be possible to determine, based on those connections, who else might have been recently exposed.
An important aspect of this approach that I alluded to is that unlike GPS that tracks actual locations, this Bluetooth-based approach only tracks other smartphone users in their proximity but does not know the physical location of the phone. This might be a critically important aspect of the design of the solution that would allay the fears of people who feel strongly about protecting their privacy. I look forward to seeing the implementation of both phases of this collaboration, and the timing of this collaboration is good because I am optimistic that in the coming weeks/months we can shift from mitigation back to containment.
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