We've had some issues lately of users sending out virus emails. I have read about using export-mailbox to search across multiple mailboxes, but it seems that it moves anything that matches the search criteria to another folder. What I'd like is to be able to send a copy to another folder, leaving the original message intact. Is this possible?

The items in the source mailbox are not deleted unless you use the DeleteContent switch, otherwise they are simply exported from the mailbox.