virus

“Virus”? No. Far more mundane. You were offered a calendar—events and notifications and such—from some website, and accepted the offer and subscribed to the calendar. This advertising calendar happens to be filled to events with phrases that are intended to scare.

Here? You need only delete a subscribed calendar that you no longer wish to subscribe to. For details, click or tap > Delete spam calendars and events on iPhone - Apple Support

Lots of these social-engineering scams around, too. Click or tap > Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

Or tap the Calendars button at the bottom of that image, find the subscribed calendars block, and find the orange-colored subscribed calendar, tap,the information ℹ️ button to the right of the subscribed calendar, scroll down, and select delete.

You don't have a virus. You chose to install a rogue calendar by tapping on a link.

iPhone/iPad with iOS13 and earlier: Settings > Passwords and Accounts

iPhone/iPad with iOS14: Settings > Calendar > Accounts

Look for a calendar subscription you don't recognize. Tap the unknown calendar and choose to delete it.