Cerebral spinal fluid (CSF) shows an increased cell count (pleocytosis), with a dominance of neutrophils and increased protein.
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. State public health and reference laboratories offer IgM assays of serum or CSF. EEE can be confirmed from acute and convalescent neutralizing antibody testing of specimens.
