Since the world began its battle against the outbreak of Covid-19, mobile apps have promised to do it all: pinpoint infections, predict who may be at highest risk, learn how long the virus survives on surfaces, estimate the fraction of asymptomatic carriers, target medical resources, prevent people from being exposed, the list goes on. And while some mobile apps can indeed be useful as we adapt to life with this virus, there is also evidence that by skewing our understanding of this disease, certain apps are more harmful than helpful.
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Kaiser Fung has been the data science lead at various companies. He is the author of Numbers Rule Your World. You can find all three installments of his comprehensive review of this study on his blog, Junk Charts.
Currently, there are no fewer than seven major Covid-19-related apps in the US, if we count only those backed by governments or reputable health care organizations. Most will, of course, attract few users and fade away—but there is one mobile app that has already garnered attention for its surprising discoveries. The COVID Symptom Tracker was first launched in the United Kingdom by a research team at King’s College, and it has been promoted in the US by Harvard and Stanford Medical Schools. The Symptom Tracker boasted over 1.6 million downloads in its first week of launch in late March. The response was so rapid and remarkable that the researchers needed just five days of data to fire off the first preprint of scientific findings. But if the initial analytics coming out of the COVID Symptom Tracker are a sign of what’s to come, then app developers have much heavy lifting ahead as they battle a large volume of low-quality data.
Each day, users of the Covid Symptom Tracker are asked to file a report of their health. They can also see an estimate of cases in their area. The app offers a self-diagnosis of Covid-19, which is not necessarily accurate but undoubtedly useful while testing is triaged and rationed by governments. (Facing a shortage of diagnostic testing, both the UK and the US governments have restricted tests to people with severe symptoms.) An undesirable side effect of targeted testing, however, is contaminating the data feeding downstream analytics, such as estimating the population prevalence of Covid-19 and identifying the most relevant symptoms. This harm is laid bare in the preprint of scien
