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 U.S., researchers evaluated 26,429 patients aged ≥18 years 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%; P=0.0245). 

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

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