The CSF from a patient infected with SLEV demonstrates a lymphocytic pleocytosis and an increased protein. The virus is very difficult to culture; therefore, the best method for an accurate diagnosis when symptoms are consistent is a positive IgM immunoassay on serum or CSF. These tests are available commercially or the test can be performed in state public health laboratories or the CDC. Positive test results should be confirmed by acute and convalescent IgG neutralizing antibody tests.
