![[ Visit Client Website ]](images/banner.jpg)
BACKGROUND: Encephalitis is an inflammatory process of the brain associated with neurologic dysfunction. Illness is generally severe and often requires hospitalization. Improving our understanding of the epidemiology of encephalitis could complement clinical management and inform public health interventions. We analyzed hospital discharge data to evaluate the burden of encephalitis in the United States.
METHODS: Encephalitis–associated hospitalizations during 1998 through 2010 were analyzed retrospectively using the Nationwide Inpatient Sample, a nationally representative sample of hospitalizations. An encephalitis–associated hospitalization was defined as a hospital discharge record with an International Classification of Diseases, 9th revision, Clinical Modification code for encephalitis listed among the top 15 diagnoses. Using the Healthcare Cost and Utilization Project weighting methodology, robust national estimates of the number of encephalitis–associated hospitalizations were calculated. SUDAAN software was used to generate standard errors (SEs) and 95% confidence intervals (CIs). Etiology and outcome of encephalitis–associated hospitalizations were examined.
RESULTS: An estimated 263,352 (SE: ± 3017) encephalitis–associated hospitalizations occurred in the United States during 1998 through 2010. A fatal outcome occurred in 5.8% (95% CI: 5.5%–6.0%) of all encephalitis–associated hospitalizations and in 10.1% (95% CI: 9.2%–11.2%) and 17.1% (95% CI: 14.3%–20.4%) of encephalitis–associated hospitalizations in which codes for HIV and tissue/organ transplant were listed, respectively. The proportion of encephalitis–associated hospitalizations with a known encephalitis cause and those for which the cause was unexplained were similar: 50.3% (95% CI: 49.3%–51.2%) and 50.3% (95% CI: 49.4%–51.3%), respectively.
CONCLUSIONS: Encephalitis is a major public health concern in the United States and should be monitored. Some of the unexplained encephalitides may be due to novel infectious and noninfectious etiologies.