An increased cell count (pleocytosis) with a dominance of neutrophils and increased protein are seen in cerebral spinal fluid (CSF).
The virus is difficult to culture from clinical specimens, but polymerase chain reaction (PCR) can be positive from both CSF and brain tissue.
Serology is the primary method of diagnosis. IgM assay of serum or CSF is available from state public health and reference laboratories. EEE can be confirmed from acute and convalescent neutralizing antibody testing of specimens.
