It is recommended that the International Committee on Taxonomy of Viruses (ICTV) be used in conjunction with writing up articles. The database contains up-to-date information from the leading source of viral taxonomy.
Absolutely! If you have an artistic flair, you could clean up a messy page or create a new template. You could also help to proof-read edits to give scientists feedback on how easy their writing is to understand from a layman's point of view. You could tag messy articles for the project, identify new stubs or even just spread the word about this WikiProject!
2) How can I get involved?
If you feel like participating in this WikiProject, please sign your name over at the members page and check out the Open Tasks to be completed.
3) At what level is it worth having a separate Wikipedia article for a particular virus?
Simply put, any level you like. If we write individual articles for all the viruses known to man, it may take a while; However, if you feel like writing an article about some particularly obscure virus that most people have never even heard of, go for it! The more the merrier :-) As a general guideline though, combine several species or subspecies into a single article when there isn't enough text to make more than short, unsatisfying stubs otherwise. If the article grows large enough to deserve splitting, that can always be done later. It's always a good idea to avoid creating articles that are doomed to be stubs.
4) What about eradicated viruses?
Like smallpox? Sure, why not! There seems to be no reason to exclude any viruses as long as somebody's willing to write an article for it.