Listeria monocytogenes encephalitis mimicking West Nile encephalitis

We present a case of a 50-year-old man who presented to Winthrop-University Hospital in the midst of the 2002 West Nile encephalitis (WNE) outbreak with the cardinal clinical findings of WNE, ie, fever, encephalopathy, weakness, and muscle tremors. During the summer of 2002, several cases of aseptic meningitis/viral encephalitis were admitted to our emergency room weekly. In addition, cases of WNE were being admitted at the same time. During this period we had 3 cases of WNE. Our patient presented with the clinical findings of WNE. However, laboratory and radiologic findings suggested the possibility of Listeria monocytogenes encephalitis. The cerebrospinal fluid findings included red blood cells, which, in the absence of a traumatic tap or HSV encephalitis, argue against the diagnosis of WNE but are consistent with L. monocytogenes encephalitis. Computed tomography scan showed communicating hydrocephalus, which also suggests the possibility of L. monocytogenes and argued against the diagnosis of WNE. Clinicians should be vigilant for the mimics of WNE in geographical areas where WNE outbreaks are occurring.