I keep getting a message on my iPhone it may have a virus

Where are you seeing this message?

Is it coming from safari? - Clear the history and cookies from Safari on your iPhone, iPad, or iPod touch - Apple Support

Is it coming from the calendar? Delete spam calendars and events on iPhone - Apple Support

There is no known virus or malware that affects non-jailbroken iPhones. However, there are people who want to trick you into thinking your device is infected.

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support