33 million Californians may not leave their homes unless it's essential

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

How phones can alert you to COVID-19 exposure

More than 8.1 million people in the U.S. have turned their iPhones and Android devices into pandemic contact-tracing tools, but it hasn't been of much use when their neighbors, classmates and coworkers aren't on the same system.