• Original Reporting
  • Sources Cited
Original Reporting This article contains new, firsthand information uncovered by its reporter(s). This includes directly interviewing sources and research / analysis of primary source documents.
Sources Cited As a news piece, this article cites verifiable, third-party sources which have all been thoroughly fact-checked and deemed credible by the Newsroom in accordance with the Civil Constitution.
This is a 3D print of a SARS-CoV-2 virus particle. SAR-CoV-2 is the coronavirus that causes COVID-19. The virus surface (blue) is covered with spike proteins (red) that enable the virus to enter and infect human cells. (Provided by the National Institutes of Health)

More than 500,000 Coloradans have already signed up for the state’s new tool to notify people if they have possibly been exposed to the coronavirus.

The tool, called Exposure Notifications, runs in the background on smartphones to exchange non-personally identifying information with other phones it comes near that also are running the app. If a person later tests positive for coronavirus, they will have the option of sending a notification to all the people who also use the app that the person had potentially exposed.


The latest from the coronavirus outbreak in Colorado:

  • MAP: Cases and deaths in Colorado.
  • TESTINGHere’s where to find a community testing site. The state is now encouraging anyone with symptoms to get tested.
  • VACCINE HOTLINE: Get up-to-date information.


Coloradans began receiving alerts on their phones on Sunday that the app is either available to download or turn on. By Wednesday night, 587,615 people had done so. That represents about 10% of Colorado’s population, said Sarah Tuneberg, the state COVID-19 adviser who has helped develop the state’s version of the app in conjunction with tech companies Apple and Google.

“That’s a huge win for Colorado already and everybody who did it,” she said during a Thursday call with reporters.

Colorado officials hope the app will greatly improve their contact-tracing efforts, during a time when state and local health authorities are struggling to contain a surging number of COVID-19 cases.

On Thursday, Pueblo Mayor Nick Gradisar imposed a 10 p.m. curfew on the city for two weeks in an effort to slow the virus. The move came one day after state officials announced that they were moving multiple counties, including Denver, Adams and Arapahoe, to more restrictive levels on the state’s COVID-19 “dial.” The more restrictive statuses come with decreased capacity for businesses and other venues.

Gradisar said he imposed the curfew to try to keep Pueblo from also moving to a more restrictive status for businesses — or even being hit with a new stay-at-home order.

“I’m not asking you to do this for me,” he said in a statement to his city. “I’m asking you to do this for our businesses and schools.”

Contact-tracing help

One of the pillars of the state’s response to coronavirus is contact-tracing — the age-old practice of asking infected people who they have been in contact with and then chasing possible new infections down through those social chains. State health officials hope the app will make this easier, both by quickly reaching potential contacts but also by reaching people whose names the infected person doesn’t know. 

People using the app who test positive will still need to be contacted by health authorities in order to get the information required to send out an alert to their contacts.

People who may have been exposed to the virus will get an alert on their phone that tells them when they may have been exposed, but it won’t tell them where the exposure occurred or who the person is who exposed them. The alert will advise them to isolate and also provide information on where they can get tested.

Tuneberg said “a huge number” of people had already used the app in Colorado to send notifications to those they may have exposed to coronavirus, but she did not have a more precise figure.

She said the app doesn’t store personally identifying information or track where you’ve been — part of what she said is Colorado’s “privacy-forward” approach to the tool. Because it mostly uses Bluetooth technology and only needs an internet connection to send out or receive an exposure notification, it also doesn’t use a lot of mobile data.

This video shows what it would look like to receive a notification alerting you that you may have been exposed to coronavirus. (Provided by the Colorado Department of Public Health and Environment)

Newer iPhones only

To use the app, people with phones running Google’s Android operating system need to download the free Exposure Notifications app from the Google app store. People with newer iPhones have the functionality pre-installed on their phones and can turn it on for free under their Settings menu.

Tuneberg said the app will work on 99% of Android phones currently in use. But people who own iPhones older than the 6S, which was released in 2015, won’t be able to use it because their phone’s operating system isn’t new enough.

State officials estimate that 81% of Coloradans own a smartphone, but Tuneberg said it’s unclear how many of those people have iPhones too old to use the app.

“We continue to work really hard with Apple to understand how many people that is and also work with them and encourage them to ensure that this service is available for everybody who has an iPhone, not just 6S or newer,” Tuneberg said.

Sarah Tuneberg, Gov. Jared Polis’ coronavirus innovation response team lead, talks about the “EN Express” service that will be available to Coloradans in the coming weeks. (Jesse Paul, The Colorado Sun)

She said people don’t need to wait until they receive a push notification on their phone about the app. But, if they would prefer activating the app by following the instructions contained in the push notification and they haven’t gotten one yet, they should check to make sure they are running the most up-to-date operating system for their phone. When all else fails, Tuneberg said to try turning your phone off and then back on again.

More information about the app is available at

Tuneberg said the state hopes everyone who can will enable the service, but she said there’s no hard goal for how many people need to sign up for the service to be successful. Every contact traced and future exposure prevented is its own win, she said.

“The more people who are in this, the more people who add their phone to the fight against COVID, the more protection we all get,” she said.

John Ingold

John Ingold is a co-founder of The Colorado Sun and a reporter currently specializing in health care coverage. Born and raised in Colorado Springs, John spent 18 years working at The Denver Post. Prior to that, he held internships at the Rocky Ford Daily Gazette, the Colorado Springs...