Many lists are set up to reply to the whole list, not the person who sent the message. If the message you are forwarding starts with one of those words, add some text of your own before forwarding it. Viruses are getting more sophisticated all the time. Increasingly, virus warnings are sent as chain letters. Often, they falsely claim to originate with some organization or government agency such as the Federal Communications Commission.
Chain letters are illegal if they ask for money or anything of value.
They're also damaging because they expand exponentially and quickly clog up valuable space. Do not just forward the message on. The same code of courtesy and good manners applies to e-mail as to messages delivered by telephone, on your personal notepaper or face to face. It's one thing to be lax among ourselves, it's quite another to be lax when we send e-mail to the public or external colleagues. Short messages can be quickly read and responded to.