SACRAMENTO, Calif. (AP) — California Gov. Gavin Newsom on Monday announced a voluntary smartphone tool to alert people of possible coronavirus exposure as cases surge higher, new restrictions are imposed and many people said they won't heed the pleas to stay home.

The tool — which has been used on a pilot basis on some state university campuses — doesn’t track people’s identities or locations but uses Bluetooth wireless signals to detect when two phones are within 6 feet (1.8 meters) of each other for at least 15 minutes, officials said.

California's 40 million residents can opt in to the system starting on Thursday. When someone who has activated the technology tests positive for the virus, that person will receive a verification code from state health officials that can be used to send an anonymous alert to other users who may have been exposed over the past 14 days.

"The more people that participate in it, the more that opt in, the more effective this program can be," Newsom told reporters. “We are hoping there will be enough to make this meaningful.”

Sixteen other states, plus Guam and Washington, D.C., have already made available the system co-created by Apple and Google, though most residents of those places aren’t using it. The tool has been used on a pilot basis on University of California campuses, where 250,000 people opted in for notification of virus exposure.

The technology comes as coronavirus cases are exploding in California and more than 80 percent of the state’s residents are under orders not to leave their homes for at least the next three weeks except for essential purposes.

Over the past two weeks, California has reported a quarter of a million positive virus cases. The 7-day average for new virus cases on Monday neared 22,000, a 50 percent increase over the prior week, state data shows.

More than 10,000 people were hospitalized in California Monday with COVID-19, including more than 2,300 in intensive care, Newsom said.

Newsom’s administration issued the stay-at-home rules shuttering restaurant dining, salons and playgrounds in Southern California and a large swath of the state's Central Valley agricultural region after more than 85% of beds in intensive care units were occupied in those regions.

Five San Francisco Bay Area counties voluntarily joined the rules, saying they didn’t want to wait until their ICU capacity dropped too low to take action. Those restrictions will last until Jan. 4, a week longer than the state’s timeline.

Ten months into the pandemic, most of the state is now back to where it started with the stay-at-home rules.

But unlike in March, when the pandemic was in its infancy and California was the first state to impose such rules, fewer people are likely to obey them.

Some business owners said they would keep their doors open and several law enforcement agencies have said they have no plans to enforce the rules and are counting on people to voluntarily wear masks and practice physical distancing to protect themselves and their families.

Californians will be able to activate the new “exposure notification” tool in their iPhone settings or on Android phones by downloading the CA Notify app from the Google Play store. Many residents will get a notification Thursday inviting them to participate.

The encounters are temporarily logged in a way that doesn’t reveal a person’s identity or geographic location.

The recent rise in infections began in October and is being blamed largely on people ignoring safety measures and socializing with others.

___

Taxin reported from Orange County, Calif.