How Contact Tracing Apps Work

Find out if you were exposed to a virus

Private companies are collaborating with government agencies to develop mobile apps for tracking the spread of infectious diseases like the coronavirus. Learn about how contact tracing apps work and what happens if you've been exposed.

What Are Mobile Contact Tracing Apps?

Contact tracing refers to the process of identifying people who have been in contact with an infected individual. Traditionally, public health officials have conducted one-on-one interviews with infected persons to track and contain the spread of communicable illnesses such as measles and E. coli. Because many people cannot recall or don't wish to disclose everyone they've been in contact with during the weeks prior to testing positive, information collected from such interviews do not catch all potential exposures.

A doctor wearing protective gear examines a coronavirus covid 19 test tube in a laboratory.
 Hocus-Pocus / GettyImages

Because nearly everyone now carries a smartphone, mobile contacting tracing apps make it possible to record the movements of millions of people simultaneously. Such apps rely on Bluetooth for contact tracing. When you download and run a contact tracing app, your smartphone broadcasts short-range Bluetooth signals, called “chirps," to communicate with other devices running the app. If a user tests positive, they can notify all other users who they've been in contact with.

What Happens if You've Been Exposed?

When a user tells the app that they have tested positive, all other users who have been within Bluetooth-distance of that individual will receive a notification that they have been exposed. The message will include information about what steps they should take to self-quarantine and get tested.

What to Do if You Have a Positive Test Result

If you test positive for certain infections, such as the COVID-19 novel coronavirus, a public health official will ask questions about where you've been and who you've been in contact with since you became infected. If you've been running a contact tracing app, you can also let other users know that you tested positive and upload the Bluetooth data stored on your phone. No identifying information about you will be shared; other users will only be told that they've been exposed.

What Are The Privacy Concerns of Contract Tracing Apps?

Since governments have the authority to track the spread of infectious diseases, they may be able to legally compel companies to hand over the data they collect, which raises civil rights and privacy concerns about contact tracing apps. While individual use of contact tracing apps is voluntary, governments could require businesses to run contact tracing apps on a device to track the movements of customers and employees.

There are also cybersecurity concerns since information stored in public databases can be hacked, potentially exposing sensitive health information that is protected under the law. Additionally, there's always the fear that companies will sell the data they collect to third-party advertisers.

Using contact tracing apps in conjunction with privacy apps for Android and iPhone can help keep your personal data secure.

How Are Contact Tracing Apps Regulated?

Countries are taking different approaches to the regulation of contact tracing apps. In the U.S., Apple and Google have collaborated with government cybersecurity experts to develop privacy protocols for Android and iOS devices. These protocols are considered "decentralized" because all app data is stored directly on the user's phone. User information only gets uploaded to the public database if the user chooses to share it.

Some governments, including the U.K. and France, have instead opted to develop their own apps for contact tracing. This approach is considered "centralized" because all user data is collected in a government database. That way, when someone tests positive, public health officials are immediately able to trace their recent contacts.

Limitations of Contact Tracing Apps

Contact tracing apps can only be effective in slowing the spread of infections if people use them and keep them running at all times. Since contact tracing apps require constant use of the phone's battery and Bluetooth capabilities, they could possibly interfere with other apps and processes.