“If you don’t pick someone up from the same home, I don’t know what to say to them,” Mayor Craig said.
In a statement, Steph Hannon, Google’s senior director of product management for exposure notifications, said that there were “known challenges with using Bluetooth technology to approximate the precise distance between devices” and that the company was continually working to improve the precision.
Company policies have also influenced usage trends. In certain US states, for example, iPhone users can activate one-click exposure notifications, simply by activating a feature in their settings, but Android users must download a separate app. As a result, about 9.6 million iPhone users in California had turned on notifications as of May 10, the state said, far surpassing the 900,000 app downloads on Android phones.
Google said it had built its system so that states would work on the widest range of devices and be implemented as quickly as possible.
Some public health experts acknowledged that the exposure alert system was an experiment in which they, and the tech giants, were learning and making improvements as they went along.
A problem they discovered early on: To prevent false alarms, states verify positive test results before a person can send exposure notifications. But local labs can sometimes take days to send test results to health agencies, limiting the ability of app users to quickly alert others.