In April, Google and Apple launched software that state health authorities can use to build COVID-19 contact tracing apps. But fewer than half of U.S. states have taken advantage, and most people living in those states aren't putting the apps to use.
In the Mountain West, Colorado's Exposure Notifications app has had the most success, with about 20% of the state's population having downloaded it. But fewer than 3% of Wyoming and Nevada residents have downloaded their states' smartphone apps.