If it was an virus that circulates itself via email address book then it will have already done the damage anyway. Very few email circulating virus are attached to cliet writen emails. The chances are the email was sent via someone you know (you being in their address book) using a spoof email account. Don't worry too much about it, the chances are avast has removed the threat. I get hundreds of emails a day that contain similar stuff and I don't even use a virus scanner/protector. Only difference is I suppose I don't click on like from email accounts like
[email protected] :)
If even you get anything from someone regarding facebook, natwest, HSBC, faceparty, youtube etc etc the best thing to do is get to that site like you would do normally via your web browser!
Hope you get it sorted, stay protected!