Virus warning in Safari only. Real?

It's an obvious scam since iPhones can't get viruses. Also no one can know what is on your iPhone not even Apple.

Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

Double tap the Home button, then swipe upwards on the Safari preview.

Go to: Settings - Safari - Clear History.

Restart Safari.

It's a scam. Close out of it.

I've gotten these before. I'm pretty sure you have to click the "close" at the bottom, delete the tab, and erase your history.