VIRAL CAUSES OF ASEPTIC MENINGITIS: ENTEROVIRUSES

Enteroviruses remain the most common cause of aseptic meningitis in those cases in which a diagnosis is made. Approximately two thirds of all culture-negative CSF from patients with aseptic meningitis will be positive for enteroviruses by polymerase chain reaction (PCR). The most common enteroviruses causing meningitis include coxsackieviruses A and B, echovirus, and enteroviruses 68 to 71. Poliovirus is also classified as an enterovirus, but its incidence has declined greatly since vaccination. Enteroviruses are transmitted by a fecal-oral route. In temperate climates, disease is most common in the summer and early fall months, although it may occur throughout the year. Symptoms generally include nonspecific flu-like symptoms, along with fever, headache, nausea, vomiting, and meningismus. A maculopapular rash may also be seen. Focal neurologic signs are rare in the adult population.
The CSF leukocyte count is usually less than 500 cells/mm3 but may be higher. There is classically a predominance of lymphocytes, but early in the illness there may be a predominance of neutrophils. The CSF protein level may be mildly elevated, and hypoglycorrhachia, a low CSF glucose, is usually mild if present. Enterovirus may be grown in culture, but PCR can make the diagnosis more rapidly and may shorten hospitalization and courses of empiric antibiotics.
Although the clinical course in adults is usually self-limited, morbidity may still be high. In a 1998 study of the clinical course of aseptic meningitis in adults, 82% of patients were hospitalized, with an average duration of stay of 4 days and 9 days of missed work. The treatment of aseptic meningitis is primarily supportive. However, trials involving the use of antiviral agents are ongoing. One drug, pleconaril, has been shown to be effective for compassionate use and continues to be investigated in ongoing trials.
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