Clinical, epidemiological, and etiological studies of aseptic meningitis in adults

From summer to autumn, we noted the occurrence of a small epidemic of aseptic meningitis in adults. Over the last 10 years, we have encountered 203 male (mean age, 34.6 ± 15.0 years) and 157 female (mean age, 35.6 ± 16.3 years) patients with aseptic meningitis. We could identify the causative virus in 17 (81%) of 21 cases during the abovementioned months in 2012. Identification rates of the virus in the stool, cerebrospinal fluid, throat swab, and serum samples were 71%, 67%, 42%, and 5%, respectively. The etiological viruses included enteroviruses in all cases, such as echovirus type 9 (E9) in 9 cases, echovirus type 6 (E6) in 4 cases, coxsackievirus type A9 in 1 case, and unknown type of enterovirus in 3 cases. No differences in the clinical manifestations and laboratory findings were noted between E9 meningitis and E6 meningitis. In addition, we countered 14 cases of mumps meningitis, 7 cases of varicella-zoster virus meningitis and 6 cases of herpes simplex meningitis during the last 10 years; these cases did not occur as an epidemic, but occurred sporadically. Cases of mumps meningitis were noted in all seasons, and cases of varicella-zoster virus meningitis were only noted from summer to winter. The etiology of epidemic aseptic meningitis in adults could be mainly due to enterovirus infection, and its prognosis was benign.