can my iphone 7 have a virus

You cannot get a virus unless your phone has been jailbroken. Try clearing the Safari History by following the steps here:

Clear the history and cookies from Safari on your iPhone, iPad, or iPod touch - Apple Support

Unless your device has been jailbroken, then there is no virus. That is a popup from using the phone. Force closed Safari, then go to Settings>Safari>Clear History and Website Data. Power the phone off/on, then go about your browsing. You might also wish to avoid the site you were visiting when you received the popup. These are generally java scripts being run in the background of the site in question.