On the day that the United States' death toll reached 200,000 Americans, Pennsylvania Gov. Tom Wolf and Secretary of Health Rachel Levine gathered in Philadelphia’s Franklin Square to announce the state’s latest initiative in combating the coronavirus.

The pair, accompanied by Philadelphia Health Commissioner Thomas Farley, announced on Tuesday the launching of COVID Alert PA, an app that will use Bluetooth technology to alert a person when they have come in close contact with someone who has tested positive for the coronavirus.

The free app, created by Irish software firm Nearform, uses Bluetooth wireless technology to detect when two users are within at least six feet of each other for 15 minutes or more. The app exchanges a random set of Bluetooth handshakes, or Bluetooth keys, officials said Tuesday, measuring proximity, not location. Both phones must have the app downloaded.

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If an app user comes in contact with someone who later tests positive for the coronavirus, they will be alerted on their phone and have the option to talk with a public health representative. Users can also receive health information about the coronavirus like testing locations and symptoms.

It is similarly used in Delaware and some European countries, and New Jersey and New York are expected to sign on in October, Levine said. The openly sourced app’s code is fully available online to increase transparency behind how the app functions and stores and extracts data, officials said.

The identity of app users will be protected by encryption and anonymous identifier beacons that change frequently, the companies have said.

Someone who tests positive in Pennsylvania is reported to either the Department of Health or a municipal health department agency and contacted by a case investigator.

That case investigator will ask the infected person if they have the app and if they are willing to use it to notify any mobile phone users who have been in close contact with them in the past 14 days, state officials said.

If they are willing to use it, they are given a six-digit code to enter to then issue a notification, state officials said.

A person who receives a notification will get something like an alert to check the app, with instructions from the Department of Health on how to protect themselves and others, including information about staying at home, quarantining and seeking medical help.

The identity of the person who was infected is shielded from people receiving a notification, and vice versa, they said.

The Associated Press contributed to this report.