Viruses were the most common cause of meningitis and encephalitis in the United States during 2011–2014, and were treated with antibiotics for the majority of cases, according to a new study published in Clinical Infectious Diseases

In order to investigate the etiology and management of meningitis and encephalitis in the US, researchers evaluated 26,429 patients aged 18 years and older with meningitis or encephalitis according to ICD-9 codes available in the Premier Healthcare Database during 2011-2014. Fifty-three percent of patients were female and the median age was 43 years. 

Enterovirus was found to be the most common etiology (50.9%), followed by unknown (18.7%), bacterial meningitis (13.9%), herpes simplex virus (8.3%), non-infectious (3.4%), fungal (2.7%), arboviruses (1.1%), and other viruses (0.8%). 

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For most cases, empiric therapy with antibiotics (85.8%) was given, followed by antivirals (53.4%) and antifungals (7.8%). Steroids were administered as adjunct therapy in 15.9% of patients, and in 39.33% of patients with pneumococcal meningitis, with an associated reduction in mortality (6.67% vs 12.5%; =.0245). 

The longest duration of hospital stay was 13 days for fungal meningitis, 10 days for arboviral meningitis, and 7 days for bacterial meningitis; median length of stay was 4 days. 

Inpatient mortality was highest in arboviral disease at 8.9%, followed by fungal and bacterial at 8.2%; overall inpatient mortality was 2.9%. The overall readmission rate at 30 days was 3.2% with the highest rates seen with arboviral (12.7%), bacterial (6.7%), and fungal (5.4%) etiologies. 

Lead researcher, Rodrigo Hasbun, added, “Adjunctive steroids are underutilized in pneumococcal meningitis where it has shown to decrease mortality.” 

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Hasburn R, Rosenthal N, Balada-Llasat JM, et al. Epidemiology of meningitis and encephalitis in the United States from 2011-2014 [published online April 17, 2017]. Clin Infect Dis. doi: 10.1093/cid/cix319

This article originally appeared on MPR