Microsoft reportedly had to shut down it's mail server to purge the massive amount of mail generated by Melissa. If a recipient opens an infected attachment, he contracts the virus. Then, the virus sends out up to 50 infected e-mails to addresses in the recipient's Outlook address book. Windows 98 and Outlook Express are immune. All Word documents generated by an infected computer contain the virus.
Infected documents can infect other computers.
The recipient must open an attachment to contract the virus. This, and practically all e-mail viruses, are transmitted as attachments. The real damage done by this virus is that the enormous quantity of mail generated clogs up The Internet. Except for a few minor changes to an infected computer's Word macros, this virus apparently does no damage to infected computers except to replicate itself and to periodically insert a Scrabble board game related message in documents that are open. I'm outta here.