There are many reasons for elevated white blood cell counts, the most common being bacterial infections, which are usually accompanied by elevated neutrophil counts in addition to elevated white blood cell counts, and sometimes need to be combined with C-reactive protein and procalcitonin to make a comprehensive judgment. If all of these inflammatory markers are elevated, prompt anti-infective treatment is needed. A small percentage of leukocyte elevations are due to viral infections, such as epidemic hemorrhagic fever and infectious mononucleosis, which are associated with elevated leukocyte counts, but often with elevated lymphocyte counts, and usually with low C-reactive protein and calcitonin. There are also other conditions that can lead to elevated white blood cells, such as hematologic disorders, which can be clarified with a bone biopsy.