The presence of WBC and RBC in the CSF indicates a traumatic tap. Although a repeat tap may be preferable, approximately 1 WBC for every 1000 RBCs can be made. While there is no known normal value for RBCs in the CSF, an RBC may be present as a side effect of the tap or as an indication of bleeding into the cerebrospinal fluid. A rise in the number of white blood cells is an indication of infection, rarely of leukemic infiltration. Bacterial infections are associated with an increased amount of polymorphonuclear leukocytes, however, many viral infections such as meningitis and encephalitis also show a high percentage of PMNs in the acute phases of illness. Moreover, any kind of inflammation can raise the WBC count.