Today, Apple and Google announced that they’re pushing out their exposure notification technology — which lets states and countries build apps that alert people if they’ve been near someone who later tested positive for COVID-19.
But there's a key difference between apps that use Apple and Google’s technology, and what many public health officials say they need most. It's the difference between exposure notification and contact tracing.
The media, including me, has been referring to Apple and Google's project as “contact tracing.” That’s largely because Apple and Google initially described the initiative as “contact tracing” before rebranding it in late April as “exposure notification.”
This is a confusing — but very important — distinction. Exposure notifications and digital contact tracing are two different things, and choosing one or the other could change the course of the pandemic.
Exposure notification apps notify you if you’ve been near someone who later tested positive for COVID-19. Contact tracing apps let people log their location and share it with public health authorities. Some states, like Utah and South Dakota, have opted for the contact tracing apps. In today's announcement, Apple and Google said that some states were interested in exposure notifications.
The two types of apps deliver wildly different experiences. Say State A has a contact tracing app, and there's a COVID-19 outbreak in one of its big meat-processing facilities. Using location data from the app, epidemiologists mapping the outbreak would very quickly determine the location of the outbreak and how it might be spreading.
Meanwhile, State B opts for an exposure notification app. If there’s an outbreak at a meat processing facility in State B, and workers turn to the app for help, they would get a notification that someone they had crossed paths with had tested positive for COVID-19 — but they wouldn’t know where this had happened. And, crucially, epidemiologists wouldn’t know where either. It would be up to manual contact tracers, interviewing those workers later, to figure out there was an outbreak at the facility.
That’s not to say a state or country couldn't have both. But those apps would have to be separate. According to rules that Apple and Google have laid out, any exposure notification app that uses their technology can’t track locations. Their technology was built so that Apple phones and Android phones can talk to each other, and exchange the anonymous Bluetooth radio signals that power exposure notifications. Right now, Apple phones and Google phones can’t talk to each other. So if a contact tracing app that tracks location and claims to have exposure notifications, those notifications would work only between iPhones or only between Android phones.
According to Apple and Google, the apps that they are building the blueprints for work like this: Let’s say you sit next to someone. A few days later, this person tests positive for COVID-19 and uses the app to notify the people they were in contact with. You receive a notification on your phone that says something like, “You were near someone who tested positive for COVID-19. Please monitor your symptoms, and read this checklist about whether you should self-quarantine.”
A contact tracing app would work like this: Let’s say go to the grocery store, which puts you in close proximity to strangers. If you later test positive for COVID-19, you could anonymously tell those strangers that they were near someone who was infectious. Or, inversely, a stranger who tests positive could anonymously share this information with you. You can also use the location log to more accurately tell human contact tracers where you’ve been, or share it with epidemiologists who map the outbreak in aggregate.
There are app-gatekeeping choices that Apple and Google — some of the most powerful companies in the world — are making instead of public agencies. The most important choice is that an app that uses Apple and Google’s technology cannot access location services. That means an app can’t use GPS, cellphone tower, or Wi-Fi hotspot data to figure out where you are. The companies have defended the choice by saying that they want privacy to be at the heart of their COVID-19 response.
But according to public health experts, this decision has profound implications. Without knowing where infectious people are, these health workers are locked out of information that would help them enforce stricter lockdowns, allow partial reopenings, and allocate personal protective equipment to those who need it.
In other words, while exposure notification apps may be great for some uses, they aren't particularly beneficial for contact tracers and epidemiologists.
Crystal Watson, an assistant professor at Johns Hopkins Center for Health Security, told BuzzFeed News that location data could help public health officials in two ways: Contact tracers would benefit from a patient having a digital log of their movements, instead of relying on their memory. And epidemiologists could also aggregate location data to identify transmission hotspots.
“The [location] data can be useful for disease surveillance more broadly, in a de-identified way,” Watson said. “But they also need more granular data. Maybe it doesn’t need to be held by public health forever, maybe just until a person is out of quarantine should be sufficient, but then it should be aggregated in a more durable way, so they can track it over the long-term.”
Some states are working on contact tracing apps. Utah paid $2.75 million for one called Healthy Together that lets people log their movements. Meanwhile, North Dakota and South Dakota have a similar app called Care19. The Utah Department of Health told BuzzFeed News these contact tracing apps can give epidemiologists the information they need to map the virus, and officials like Utah Gov. Gary Herbert have argued that they can help the states open up safely, in stages.
But in places where they are available, not many people are using them. In Utah, just 45,000 people in the state have downloaded Healthy Together — about 1% of the state’s population.
There are upsides and downsides to both contact tracing and exposure notifications. Watson said that as public health authorities explore which options are best for them, they may need to make changes.
“We need some sort of pilot period where we see how it goes and make adjustments, because we want to make sure that this is helpful not harmful, and that people feel like their privacy is protected, and are willing to engage,” Watson said. “So we need to maybe keep adjusting as we go along and start to put them into use.”