Outbreak of aseptic meningitis caused by echovirus 30 in Kushiro, Japan in 2017

Abstract Background: Echovirus 30 (E30) is one of the most common causative agents for aseptic meningitis. Objectives: In the autumn of 2017, there was an outbreak caused by E30 in Kushiro, Hokkaido, Japan. The aim of this study was to characterize this outbreak. Study design: Fifty-nine patients were admitted to the Department of Pediatrics, Kushiro Red Cross Hospital (KRCH) with clinical diagnosis of aseptic meningitis. Among those, 36 patients were finally diagnosed as E30-associated aseptic meningitis by the detection of viral RNA using reverse transcription-polymerase chain reaction (RT-PCR) and/or the evidence of more than four-fold rise in neutralizing antibody (NA) titers in the convalescent phase relative to those in the acute phase. We investigated these 36 confirmed cases. Results: The median age was 6 years (range: 6 months–14 years). The positive signs and symptoms were as follows: fever (100%), headache (94%), vomiting (92%), jolt accentuation (77%), neck stiffness (74%), Kernig sign (29%), and abdominal pain (28%). The median cerebrospinal fluid (CSF) white cell count, neutrophil count, and lymphocyte count were 222/μL (range: 3–1434/μL), 144/μL (range: 1–1269/μL), and 85/μL (range: 2–354/μL), respectively. Although the detected viral genes demonstrated same cluster, they were different from E30 strains observed in Japan between 2010 and 2014. Conclusion: We mainly showed clinical and virological features of the E30-associated aseptic meningitis outbreak that occurred in Kushiro. To prevent further spread of E30 infection, continuous surveillance of enterovirus (EV) circulation and standard precautions are considered essential.