I cannot stress this enough. There are many people in the world who do not seem to have enough to do, are angry, experimenting or plain just don't care. These people create viruses and unleash them to the world. If you do not perform these updates, it will give you a false sense of security as you will not be protected from the newer, often more dangerous viruses. A virus is a small piece of software designed to operate on your computer without your knowledge or consent.
Most viruses are benign - they cause no damage other than annoying the operator.
Some viruses cause minor damage or embarrassment. A few of the worst can destroy a computer, erase files or disk drives, or send sensitive data to outsiders without your knowledge. Viruses are spread through infected emails, documents and programs. Sometimes this is as simple as running an attachment to an email message. Some of the newer viruses can be inserted into your system via HTML email messages.