Fig. 1.

Investigations performed to establish diagnosis by period/location, on patients with meningitis and a negative Gram stain. P value was calculated using Fisher's exact test comparing the number of tests performed in each category between patients in Houston and New Orleans. Patients with more than one test were counted only once in each category. CSF BinaxNow (Alere, USA) is a rapid immunochromatographic CSF assay. * Serology for cytomegalovirus, Mycoplasma pneumonia, Bartonella, leptospirosis, Rocky Mountain spotted fever, Ehrlichia. † Serology on CSF and serum for West Nile virus and other arboviruses (St Louis encephalitis, western and eastern equine encephalitis, California encephalitis).