By now you probably have your answer to this but anyway here goes-
2 definitions:
Virulence = Ability to cause disease.
and;
Virulent = Capable of causing disease by breaking down protective mechanisms of the host. Used of a pathogen.
I guess the possible impacts would depend on what type of virus you were discussing. Influenza, AIDS virus, adenovirus (causes common cold) are all going to posse as a different threat to society for varying reasons.
Could have major impact esp. if a pandemic were to occur (then look at what were to happen in this case) to not quite as serious - time off work, school (???). Look at economy, social impact.
But then there could be positive effects - this article might give you an idea/starting point :
http://www.newscientist.com/news/news.jsp?id=ns99994742
