No, local health authorities can utilize Exposure Notifications Express without developing or maintaining their own stand-alone app.
The second update to iOS 13 within three weeks is here. iOS 13.7 is a minor update, with undisclosed bug fixes and one significant change to the COVID-19 Exposure Notifications system. While the iOS 13.6.1 update brought iPhone users a fix to the green tint issue on some displays, iOS 13.7 mostly works behind the scenes.
In early April Apple and Google announced a joint effort to "enable the use of Bluetooth technology to help governments and health agencies reduce the spread of the virus, with user privacy and security central to the design." The two part plan began rollout in May with phase one; phase two is currently underway.
Another way to track and view cases of COVID-19 in your local area has arrived free on the App Store. COVID Nearby can be launched on the iPhone or iPad to log coronavirus symptoms and test results. Privacy is guaranteed thanks to differential privacy, a method which keeps users anonymous and reports secure. The project has been developed at Rutgers, The State University of New Jersey with support from the National Science Foundation and the National Institutes of Health.