I graduated from WVU in 2007. From what I've gathered, rush has gotten more popular in recent years (about 40 girls per fall pledge class), but total was also raised to 95 versus 90 girls.
Spring rush is only COB, and not all chatpers participate. I'd check out WVU Greek Life facebook pages (there is an overall page, and individual chapter pages) for more info about COB come spring. When I was there, sororities also places ads in the DA (the student newspaper).
I'm assuming you're talking about sorority rush.
Feel free to message me with any questions! You'll love WVU. Great campus, tons of school spirit and pride, and active Greek life. Good luck!!