According to lexicographer and dictionary expert Susie Dent, the average active vocabulary of an adult English speaker is around 20,000 words. We also have a passive vocabulary of around 40,000 words, words we have stored but don’t use. The current environment is adding to our active vocabularies. It seems every day we hear the words antibody testing, bioinformatics, community spread, computational biology, contact tracing, coronavirus, Covid-19, epidemiology, flattening the curve, N95 masks, pandemic, pathogens, personal protection equipment (PPE), serology testing, social distancing, swabs, therapeutics, and ventilators, just as a sample.

Between now and year end, the most important term in our vocabulary may turn out to be contact tracing. In combination with extensive testing, contract tracing is an important tool to counteract a potential second wave and prevent cases from spiraling upward again.

The concept behind contact tracing is simple: identify those who test positive for Covid-19, isolate them and monitor their health, and reach out to people who may have been in contact with the infected person and urge them to quarantine themselves. “In contact with” means the people who may have been within 6 feet of the infected person for more than 10 minutes, more like 5 minutes in a healthcare setting. Communication with those contacts needs to advise them to quarantine themselves and monitor their health. The goal is simple — stop the spread. The implementation is difficult.

One estimate of the scope of contact tracing in the U.S. calls for 100,000 contact tracers at a cost of nearly $4 billion. Even if they can be brought on board and trained, their task is daunting. For example, suppose, sometime in phase 3, a person tests positive and the county department of health assigns a tracer to call her. The tracer asks where the infected person has been in the last 14 days. Who had she been close to? Where had she been? If the answer is visiting a friend or relative, the tracer records the contact information and reaches out to them. That would be the easy examples. Suppose the infected person responded she had been at the shopping mall. What stores? Apple store. Who did you talk to? What time were you there? What did you touch? She called the tracer back and said she had forgotten to mention a couple of things. She had also stopped at Chick-fil-A at the Food Court and had some lunch. Also, took a walk through Macy’s and looked at various things on three floors of the store. Oh, and stopped in Bed Bath & Beyond and looked at some things. Talked to one of the sales people but don’t know their name. Oh, one more thing, on the way out of the mall, she walked through the Concourse where a number of merchants had small booths selling smartphone covers, jewelry, and other items. Don’t recall exactly, but I might have stopped at a few of them. It is easy to imagine the tracing task could overwhelm the departments of health.

Is it possible technology could help with contact tracing? I think so. I will first describe an imaginary solution to show an extreme of what might be possible, but may not be practical. Then I will describe an approach which I believe is practical.

Imagine you had an app which could perform an accurate Covid-19 test by simply touching the fingerprint reader on your smartphone or perhaps with a small attachment of some kind which could test a drop of blood you extract from a finger. The test could be done as often as you would like. If you become tested positive, the app would ask your permission to notify the public health department. They would confirm your positive test and advise you on steps to take and they would monitor your health status.

Now here comes the interesting part. Your app would detect a notification from others who have a smartphone whenever you are within ten feet of them. Your smartphone would receive an encrypted code from the other person’s smartphone via BlueTooth. Bluetooth is a wireless technology built into all smartphones. It is typically used to connect AirPods or other wireless headphones. The code you receive contains no personal information about the other person. Codes are only stored for 14 days. If you become tested positive and your smartphone has notified the public health department, the department would then notify the people who have opted in to participate in the program and let them know they have been in close contact with a person who is infected. They are advised to quarantine themselves for 14 days and to monitor their temperature and be on the lookout for symptoms.

In effect, the smartphone app, in conjunction with a public health database, have become the contact tracers. Would it work? Perhaps. To make it work would require a large number of people, perhaps 60-70%, to opt in. The whole process would have to be designed to insure privacy, and people would have to trust that the privacy protection is real and enduring. The other major assumption in this imaginary scenario is the availability of fast, easy, regular testing, which is not yet the case.

I believe there is another alternative or at least a supplement to full blown manual contact tracing. It is called “How We Feel” (HWF). HWF is a smartphone app which lets you self-report your age, sex, ZIP code, and any health symptoms you may have. It only takes 30 seconds or less to use it. Aggregate data is shared securely with select scientists, doctors and public health professionals who are actively working to stop the spread of Covid-19. The app doesn’t ask you to sign in or share your name, phone number or email address. The first time you download the app and donate your data with a check-in, HWF donates a meal to people in need through Feeding America, a nationwide network of more than 200 food banks which feed more than 46 million people through food pantries, soup kitchens, shelters, and other community-based agencies.

The HWF app was built by an independent, nonprofit organization called The How We Feel Project. The organization was founded by a volunteer team of scientists, doctors and technologists. Their mission is to make the world healthier by connecting citizens with the global health community. The organization was created in March 2020 to help fight the COVID-19 pandemic.

HWF works with scientists, doctors and public health professionals from leading institutions including The Harvard T.H. Chan School of Public Health, the McGovern Institute for Brain Research at MIT, Broad Institute of MIT and Harvard, Howard Hughes Medical Institute, University of Pennsylvania, Stanford University, University of Maryland School of Medicine, and the Weizmann Institute of Science.

I like everything I have learned about HWF, and I use it every day. HWF is collaborating with Dr. Gary King from Harvard University’s Institute for Quantitative Social Science’s Privacy Insights Project. Dr. King specializes in developing technologies to make data available to researchers while protecting participants’ individual identities. Here is where you can get the app: