Acute, febrile CNS illnesses in an endemic area of Texas.

were obtained for serologic studies. In addition, throat swabs, stools (or rectal swabs), and cerebrospinal fluids were obtained whenever pos¬ sible for virus isolation studies. Criteria. The following criteria were used for the diagnosis of arbovirus infections. 1. Confirmed WEE or SLE cases: (a) four¬ fold rise or fall in hemagglutination inhibiting (HI) or complement fixing (CF) antibody titers between appropriately timed acute and convalescent serum specimens, or (b) HI titer of 1:160 or greater from a child less than 1 year of age, or (c) isolation of the virus from the patient.