Microsoft has issued a few patches to close some of the holes, but there are many security holes left. Microsoft Outlook is just one of many email clients available. Some of Outlook's competitors offer vastly superior features. Survey available email clients to see which has features best suited for your needs. Download directly from their website.
Several versions are offered for download, some are totally free.
Otherwise, the virus could still use the old Outlook address book to retransmit itself to everyone listed. If you suspect a message could contain a virus, simply delete the message without opening it. Outlook can, under some settings, automatically open the attachments and thereby subject your computer to instant infection. You open the email because you are accustomed to getting email from your friend. If you are also using using Outlook, the virus will immediately send itself in the same manner to everyone you have in your Outlook address book.