What Causes Fever And High WBC After Broken Bone?

Hi my father age 63 met with an accident 7 day ago & underwent operation 10 days ago . bone below the knee got broken ortho surgeons have done operation .but he is got fever , & his WBC count got increased to 11000 then Physican prescribed anti biotic then its decreased to 10,200 & then to 9,200 . but 2 day before it reached onceagain to 11000. Now pus is coming out of the leg where leg operation was done .....& my father is nervous.they are removing pus day by day(Pus came nearly aftter 7th day ) (as per doctor Pus decreased compared to earlier) . & doctor sent that pus for Testing . Pls guide whether these symptoms are dangerous ?