iPhone antivirus,

Just to add to what Roger Wilmut 1 stated:

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

This is a scam. Do no respond to it in any way nor follow any links. No-one can detect viruses remotely, and in any case iPhones cannot get a virus unless they've been jailbroken.

You can report this if it's am email by sending it as an email attachment to reportphishing@apple.com