How are you feeling today? COVID-19 symptom tracking apps want to know

At her April 8 press conference, Mayor London Breed said she had recently downloaded How We Feel, an app in which users share their zip codes and their daily symptoms. 

“I basically log in everyday,” the mayor said. “It asks me how I feel, it asks me about my activities, and it also locks in my zip code. This is really a tool that could potentially help,” she said, adding that it is being facilitated by John Hopkins University and “helps to potentially predict based on zip code the next hotspots.”

“The more people we’re tracking, and the more we know what’s going on, the better we can identify locations and figure out where there might be challenges in the future,” she added.

Indeed, tracking apps have been used in the coronavirus efforts in Israel, China, and South Korea.

While medical researchers and data scientists said such apps could be useful in finding the next hotspots, they also raise questions about data privacy. Still, there are many anxious for the apps to become widespread and Apple and Google announced last week that they would collaborate to create a Bluetooth-based contact-tracing technology.

“The more information we can get about San Franciscans, the better,” said Dr. Mark Pletcher, epidemiologist and internal medicine physician at UCSF, which unveiled its COVID-19 symptom tracking app, Citizen Science, on March 30 and has had more than 15,000 downloads and participants to date.

How We Feel, developed by a non-profit that included participants from Harvard, MIT, Howard Hughes Medical Institute (Maryland), the University of Pennsylvania, Stanford University, and the University of Maryland, has been downloaded by 170,000 users across the country.

Pletcher said the data collected “can advise our health system and that informs the models of what’s going on and what’s going to happen in San Francisco.” 

Already, Pletcher said, the data collected in its first 10 days showed that about a third of participants “have some symptom that might be consistent with a COVID-19 infection.” But, when they included only those experiencing fever or high temperature, and/or a cough or shortness of breath — symptoms more consistent with a COVID-19 infection — “only a tiny fraction of people” have shared those symptoms.

Pletcher’s colleague, Dr. George Rutherford, an epidemiologist and biostatistician at UCSF, said their analysis of the data showed that the shared symptoms “runs at half a percent” of those who report daily symptoms. “So if we see a kick up that will be pretty obvious,” he said. 

“The fever alone kind of bounces around and it’s probably less useful unless you look at it in this combination with cough or shortness of breath,” he added. “If it blips up, you say, ‘uh oh what is happening?’ and then you look at all the other stuff to see if you could start narrowing it down geographically.”

Rutherford said that they are seeing “very low rates.”

Pletcher added. “It probably means that there isn’t a lot of active transmission happening among the people that are enrolled in our study,” or, in lay terms, “a good sign.”

Dr. John Openshaw, an infectious diseases physician and researcher at Stanford University, and a scientific collaborator for the How We Feel app, said that the app also add information that is lacking because of the dearth in testing.

“With the uneven testing that’s currently a problem, it really gives us a better idea of where the disease is and what populations it’s affecting,” he said.

“The real key is getting the numbers to see trends and understand what’s going on, not only in California but throughout the country,” he said.

Openshaw said that they are currently working on analysis with the data collected now.

“If you start people reporting fever, chills, coughs in an area, that’s concerning that you have community transmission within those areas,” he said. Openshaw explained that rates of community transmission could depend on a lot of factors, including whether a city is sheltering in place and how many other respiratory viruses are circulating in that area that “might be putting noise” into their data.

He said that with the flu season ending, reported flu-like symptoms could likely be COVID-19, instead of influenza.

“To be quite honest with you, we need as many [participants] as we can get,” Openshaw said. “It would really depend on the community that you’re looking at, the amount of COVID that is in that community.”

Openshaw gave an example where How We Feel would be unlikely to detect even low community transmission in an area of 1,000 people if only a few people use the app.

“But now you have an example where 600 to 800 are using the app, then now you can see it and you can see it way earlier,” he said. “Every person who reports, increases the ability of the system to detect the disease within their community.”

Openshaw said that the goal is to understand COVID-19 better, see where cases are happening, and better inform public health officials on where resources need to be allocated.

While How We Feel only asks for a user’s zip code, Citizen Science has an optional geolocation sharing.

Pletcher acknowledged that some users might not feel comfortable sharing their location data, but many others are doing it.

“The more people use it, the more information we will have about how the epidemic is spreading,” he said.

Despite the urgency brought about by a global pandemic, the privacy implications of the app gave some city officials pause. 

“There’s clearly an appetite to solve this public health crisis with technology that under almost any other circumstance would be immediately rebuked, from ankle bracelets that enforce self-isolation orders to government-sponsored apps that track movements and trace contacts of people who may have been infected,” said District 3 Supervisor Aaron Peskin, who authored the city’s ban on facial recognition technology.

Privacy advocates caution app developers on the proper use of people’s location data only for its public health intention, and the limitations of mobile location tracking.

“As a general matter, with apps like this, the question is always: ‘Are they effective at addressing public health needs?’” said Jake Snow, a technology and civil liberties attorney at ACLU of Northern California.

Snow said that if the apps are indeed effective, app developers should make sure that information is “limited to just addressing the public health concern and not other means of extracting value from that data.”

“In this time, people are justifiably worried about their health and the health of their families and friends and communities,” said Snow. “So if an authoritative voice is recommending that they install an app, I don’t think that people should be expected to go through the laborious and confusing process of protecting their own privacy.”

“These are obviously extraordinary times,” Peskin adds. “Before we start promoting any mass surveillance tool, they should be subject to a rigorous, public vetting of their risk to members of the public.”

Pletcher clarified that although they collect individualized location data for those who opt in, that data is not available to the public.

“We’ll publish maps, which do have aggregate information in them,” he said. Public maps would include how many people have symptoms in every zip code and how many have signed up from different states.

“That kind of information we will make public because there’s an immediate usefulness in doing that, but it’s not individualized data,” Pletcher said.

Unlike other countries that already use contact tracing apps to backtrack a patient’s movements and locations, Pletcher said that Citizen Science is not doing that.

“We can’t do that and we won’t do that unless we get [Institutional Review Board] approval to do that, and approval and consent from participants,” he said.

UCSF already has access to the data collected by Citizen Science. “We are definitely open to providing day-to-day information from our study that will be useful for hospitals,” Pletcher said.

And the data is being shared with other public health officials. App developers said that people can participate in as many apps as they want, as long as they use all of them daily.

“Reporting that you feel well is just as important as reporting that you don’t,” Openshaw emphasized. “Even if you feel well, use the app, let us know, that’s really important and please use it every day.”Both How We Feel and Citizen Science (search for UCSF Eureka Research and use the study code “COVID19”) apps are available in the App Store and Google Play Store.

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