https://techcrunch.com/2020/05/20/covid-19-exposure-notification-settings-begin-to-go-live-for-ios-users-with-new-update/

Apple has released iOS 13.5, which includes support for the Exposure Notification API that it co-created with Google to support public health authorities in their contact tracing efforts to combat COVID-19. The API requires third-party apps developed by public health authorities for use, and none have yet been released, but iOS device users already have access to COVID-19 Exposure Logging global settings.

As previewed in the beta release, you can access the Exposure Logging settings under the Settings app, then navigating to the ‘Privacy’ subsection. From there, you can select the ‘Health’ submenu and find the COVID-19 Exposure Logging setting, which will be off be default. It can’t be turned on at all until you actually get an authorized app to enable them, at which point you’ll receive a pop-up asking you to authorize Exposure Notifications access. Once you do, you can return here to toggle notifications off, and also manually delete your device’s exposure log should you choose to opt out.