Apple has released iOS 13.7, which introduces a new Exposure Notifications System directly baked into the OS, to help combat the COVID-19 pandemic, meaning new system no longer requires a separate app to be downloaded. When you upgrade to iOS 13.7, you’ll see a new section of the Settings menu that includes a toggle to “Turn on Exposure Notifications.”
Apple has released iOS 13.5, which includes improved Face ID recognition of protective masks and 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.
iOS 12
Apple has released iOS 13.4 which focuses on bug fixes. Most notably, they address a problem caused by iOS/iPadOS 13.4 wherein users running that version could not join FaceTime calls with users running older versions of iOS or macOS—iOS 9.3.6 or OS X 10.11.6 or earlier, to be specific.