Private Automated Contact Tracing

An automated, Bluetooth-based system helps perform contact tracing in a private, anonymous way, offering a method to reduce disease spread during a pandemic.
a logo showing the letters P A C T with circles representing radio waves emitting from the letters.
PACT is an automated, smartphone-assisted approach that permits effective contact tracing while preserving privacy. This video shows an overview of how the system works.

Contact tracing is key to controlling the outbreak of an infectious disease. MIT Campus, Massachusetts General Hospital, and Lincoln Laboratory led the development of a framework called Private Automated Contact Tracing (PACT) that augments the manual tracing efforts of public health officials, in response to the COVID-19 pandemic. The framework relies on short-range, anonymized Bluetooth signals emitted by and picked up by smartphones. People who test positive for COVID-19 can upload the signals their phone emitted in the past 14 days to a database, and other people can scan the database to see if any of those signals match the ones picked up by their phones. If there’s a match, a notification will inform those who may have been exposed to the virus and provide further guidance from health officials.

Soon after PACT's development in 2020, Apple and Google integrated a similar framework into their jointly created Exposure Notification System. The system has been enabled on millions of smartphones worldwide and has resulted in hundreds of thousands of exposure notifications. It has also been integrated into official contact tracing efforts in many U.S. states.

To access any of the PACT datasets, you can visit or

An screengrab from the video showing about a dozen robots in a large room (representing humans at a party)
Learn more about how our researchers assessed the sensitivity and accuracy of PACT's Bluethooth-based exposure risk estimations.