Virus on calendar

It basically means that you have exposed your address somewhere.

1. Go to your iCloud Calendar page via a desktop browser.
2. Click the gear icon in the lower-left corner, click Preferences > Advanced.
3. In the Invitations section, change the option from In-App Notifications to Email to iCloud Address.

You can also tap on this Event and report it Junk. This will remove the event and won’t notify the sender.

See: Spam in my calendar - Apple Community

This is not a virus. This is basically spam.

What calendar are you using? Google? iCloud?

I got the same things too but I really don know how to delete it

iPhones cannot be hacked or infected with Virus / Malware / Spyware by merely clicking on a link in Safari, unless you have intentionally downloaded spurious softwares or unauthorised apps directly from internet and installed on your iPhone or/and have Jail Broken.

You need to look at the way you share your sensitive and valuable informations of your device with your friends and family members.