OLYMPIA, Wash. (AP) — Washington state on Monday launched a statewide coronavirus exposure app, joining more than a dozen states that have already enlisted the use of smartphone technology in the ongoing effort to prevent the spread of COVID-19.

People with iPhones can now enable the ‘exposure notifications’ feature that is already in their phone’s settings, and Android devices can download the app, called WA Notify. Use of the app is voluntary and users can opt out at any time. The statewide expansion comes after a monthlong pilot project used by 3,500 participants — including students, faculty and staff — at the University of Washington.

“This offers Washingtonians another tool to help control the pandemic,” state Secretary of Health John Wiesman said of the program.

The technology, created by Apple and Google, is in use in more than 30 countries and more than a dozen states in the U.S., including New York, Colorado and Virginia. Washington was among five states with pilot programs already testing the technology.

Wiesman cited modeling for King, Snohomish and Pierce Counties done by Oxford, Stanford and Google that predicted significant decreases in both infections and deaths if at least 15% of people use the app. Washington officials are hoping to exceed that 15% threshold.

At a news conference announcing the app, Gov. Jay Inslee said more than 200,000 people had already signed up since it went live that morning.

“A lot of people do understand the benefit of this,” Inslee said.

Health officials said that when thinking through how many people might use WA Notify, it was estimated that Washington’s age 18 and up population is about 5.4 million, of which about 3.6 million are believed to have smart phones. Based on the early interest so far, officials believe that the minimum goal of 540,000 people participating will be exceeded.

The app uses Bluetooth wireless technology to detect when someone who downloaded the app has spent time near another app user who later tests positive for the virus. Phones using WA Notify exchange random codes, which officials said are completely anonymous, with no location tracking or exchange of personal information.

When someone tests positive for the virus, a health official will ask them if they have WA Notify and will give them a verification code — which is not tied to their identity — to enter into the app. Once entered, the app can determine users who have been near the person who tested positive and notify them of possible exposure. No information about who may have exposed them or where the exposure occurred is included in the notification. The notification will direct people to a website with information on next steps, including how and where to get tested.

“I think the really important thing we want the public to understand is that WA Notify doesn’t need to know who you are or where you go in order to work,” said Lacy Fehrenbach, the Department of Health’s deputy secretary for COVID response. “The more people that adopt this technology, the more effective it is.”

The app — which can only be used on smartphones, not tablets — is meant to be used to complement contact tracing that is already being done by the state and local health departments.

“This is an anonymous supplement to our contact tracing system, it is not a replacement,” Fehrenbach said.

After a person tests positive for the virus, a contact tracer gets in touch with the person to determine where they have been and who they have been around in order to ensure that close contacts are notified and told to get tested and self-quarantine.

Officials said that the benefit of the app for is situations where a person who tests positive doesn't know the people they were around, for example on a bus. If others on that bus have the app, they will be notified about the potential exposure within 24 hours of the COVID-positive user entering their verification code into their app.

The statewide rollout of the technology comes as the state has seen a sustained spike in new cases and hospitalizations.

As of this week, more than 165,000 cases have been confirmed statewide and there have been 2,774 deaths.

Nationwide, there have been more than 267,000 virus-related deaths and over 13.5 million confirmed infections.

Governors have been told that they can expect a first batch of the coronavirus vaccine by mid-December, but officials caution that all of the other tools like masking and social distancing remain important since the majority of the population won't have access to the vaccine until sometime next year.

“That’s obviously going to be quite a long process before everyone can get vaccinated,” Wiesman said. “But these are the things we can all do now to take care of ourselves.”

For most, the coronavirus causes mild or moderate symptoms, such as fever and cough that clear up in two to three weeks, although long-term effects are unknown. But for some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia and death.