This fall, the University of Washington plans to test smartphone technology that tells users if they may have been exposed to the virus that causes COVID-19.

Depending on how that pilot program goes, it could become available throughout Washington, said state Department of Health spokesperson Cory Portner.

The Exposure Notifications System for iPhones and Android phones uses Bluetooth technology developed by Apple and Google to detect proximity to other phones. If someone who has enabled these notifications tests positive, they can anonymously and confidentially notify other users who have been within 6 feet of them.

“If you opt in to use the app and receive notification that you’ve been potentially exposed, the message will help you connect with public health to get recommendations on next steps,” DOH spokesperson Jamie Nixon said.

The design is aimed at preserving privacy by not collecting location data or sharing users’ identities, which might help people feel comfortable using it, but which also hinders efforts to track its usage and effectiveness.

The University of Washington’s pilot program could begin in October, UW spokesperson Victor Balta said. The university hasn’t yet determined whether it will include all of UW’s campuses, students, faculty and staff, Balta said.

Washington’s exploration of this technology is part of a larger effort with Oregon, California, Nevada and Colorado to work together on a response to the pandemic — an agreement known as the Western States Pact. Nevada and Colorado already launched their apps, as have a handful of other states, including North Dakota, Wyoming, Alabama, Virginia, North Carolina, Delaware and Pennsylvania. Guam, a U.S. territory, has an app as well.

If multiple states use the Exposure Notifications System, travel among states could be safer, especially for people moving between border cities such as Vancouver and Portland, Nixon said.

“In the absence of a strong national strategy to fight COVID-19, coordinated efforts between states on reining in this pandemic are critical,” Washington Gov. Jay Inslee said in a news release from California Gov. Gavin Newsom.

The U.S. doesn’t have a national tracing app.

Other countries have been using Bluetooth technology to notify people of potential exposure to SARS-CoV-2, with varying levels of participation by the public. In Europe, the adoption rate ranges from about one-third of the population in Finland and Ireland, to 22% in Germany and a meager 4% in France.

Places that have had the most success in getting people to voluntarily use virus-tracing apps tend to be smaller countries in Northern Europe where trust in the government tends to be higher and where people are comfortable with new technologies. Finnish users have said they felt it was a civic responsibility to install their country’s app.

More intrusive approaches — such as France’s app, which has a centralized data-storage system criticized by privacy activists — have been less successful.

“The privacy issue is a political choice,” Sean L’Estrange, a social scientist at University College Dublin who has studied testing and tracing, told The Associated Press. “To the extent you can maximize privacy, you increase the credibility of the app because it won’t arouse suspicion.”

An Oxford University study published several weeks ago on the preprint server MedRxiv found that even a low adoption rate for a contact tracing app can have a positive effect. The model used by the study’s authors found that if 15% of a population used the technology, infections were reduced by 8% and deaths by 6%.

Nevada saw 20,000 downloads of its app soon after launching Aug. 24, Julia Peek, Nevada’s deputy health administrator, told the Associated Press. Nevada’s population is a little more than 3 million.

Exposure notification technology is meant to complement existing case and contact tracing efforts, Nixon said.

Contact tracing is the process in which public health workers call people who test positive for a virus, find out who they’ve been around, and then calls those contacts to encourage them to get tested, too. It has long been used when dealing with outbreaks of infectious diseases.

Washington is falling short of its case and contact tracing goals, according to a DOH report released last week. DOH case and contact investigators have reached 49% of newly diagnosed people within 24 hours of a positive test; the agency’s goal is 90%. Within 48 hours, they’ve reached 70% of people who have been in close contact with an infected person; the goal is 80%.