Ignore it (after deleting it that is).
Many emails that have contained viruses usually have forged email from addresses. Some dumb anti-virus programs actually send warnings to the supposed sender.
The email probably came from someone you don't even know as you and their email address were in someone else's address book.
Some can actually be trying to deceive you into clicking on a link or opening an attachment in order to remove the virus (infecting you, not cleaning the computer).
Trust in avast to stop incoming infection and stop outgoing infected email (if ever required, because nothing in life is 100% guaranteed).
