Microsoft Office macro viruses will sometimes make your Office programs behave erratically, such as not allowing you to save a document except as a template. Worms can have a severe impact on computer networks. The major problem the Melissa and Loveletter viruses created was the volume of spurious e-mail they produced. They overloaded networks, which then couldn't handle the delivery of regular mail. Long-term consequences of viruses can vary.
Many viruses leave no residual damage at all.
However, there are also quite a few that can create serious problems. Some macro viruses corrupt Office files. The chances of recovery can range from complete to incomplete to not at all. More seriously, some viruses don't limit themselves to just a few types of files. Data recovery from this type of virus can be extremely difficult or even impossible.