2012 West Nile Virus Outbreak - Who Were the Critically Ill Patients?

Abstract

PURPOSE: The West Nile Virus Outbreak in 2012 demonstrated high acuity. The City of Dallas, Texas reported 118 hospitalizations; 37 required ICU admission (31%). Characteristics and outcomes of patients requiring admission to an ICU should be identified. METHODS: A database at our institution was created compiling information from patients designated to have West Nile Virus (WNV) infection. Thirty-five percent of patients (19/55) required ICU admission; these were further analyzed to identify demographics, frequency of certain co-morbidities and complications, WNV diagnosis and outcome. RESULTS: Of the 19 patients admitted to the ICU, 63% were men; ages varied from 38 to 81 years; 11 were White, 3 were African American, and 5 were Latino. Notable co-morbidities included hypertension (63%), diabetes (36%), and chronic kidney disease (21%). All reported subjective fever; 42% reported headaches. Encephalopathy was noted in 84%, seizures in 47%, acute flaccid paralysis in 10% and myoclonus in 5%. An elevated cerebral spinal fluid (CSF) white blood cell count was noted in 63%, although not all patients underwent lumbar puncture. Notable complications included acute kidney injury (AKI) (42%), acute respiratory failure (ARF) (42%) and transaminitis (10%). Patient diagnostic evaluation was not uniform. Available serum studies noted 89% were IgM positive and 50% were IgG positive for WNV antibodies. Available CSF data revealed 37% had positive CSF WNV IgM antibodies. Of the case definition classifications for West Nile disease, 16% had «confirmed» West Nile Neuroinvasive Disease (WNND), 47% had «probable» WNND, 21% had «possible» WNND, 5% had «probable» West Nile Fever (WNF) and 10% had «possible» WNF. Disposition was noted to be home (32%), Rehab or Long Term Acute Care (26%) and death (42%). CONCLUSIONS: Analysis revealed white men were disproportionately affected and there was a notable association with ICU care in patients with hypertension, less so with diabetes and kidney disease. Neurologic symptoms were prominent, with encephalopathy more frequent than seizures. Significant complications were AKI and ARF. The mortality for WNV and ICU admission was high at 42%. A limitation in more in-depth analysis was the lack of uniform diagnostic evaluation.