Etiology of viral meningitis outbreak in Dongtou, Zhejiang, 2015

Objective An outbreak of suspected viral meningitis occurred in Luxi village, Dongtou district, Wenzhou prefecture, Zhejiang province, in November 2015. In order to identify the pathogen, we analyzed the molecular characteristics of the pathogen and traced its origin. Methods Epidemiological investigation was conducted. A total of 140 samples, including throat swabs and stool samples, were collected from 32 patients and 75 close contacts. Human enterovirus (HEV) nucleic acids was detected and the viruses were isolated. We sequenced the VP1 gene region of HEV isolates and did the homology and evolution analysis. Results There were 396 students in Luxi primary school and kindergarten, and 32 children were affected, the attack rate was 8.1%. The main clinical symptoms included fever, headache and vomiting. Thirty (93.8%) HEV nucleic acid positive samples were detected in 32 sick children, while 5 (6.7%) HEV nucleic acid positive samples were detected in 75 close contacts. Twenty three strains of echovirus 30 (ECHO30) were isolated. The nucleic acid and amino acid of the isolates shared 99.9%-100.0% and 99.7%-100.0%homologies respectively. The homologies of nucleic acid and amino acid between new isolates and prototype strain of ECHO30 were 81.8% and 92.1%. The phylogenetic analysis showed that the new isolates belonged to ECHO30 genotype cladeⅠ, which were close to both CHN/ZJ/RA-72/2013 isolated in 2013 and ZJ/JH Chen/2014 isolated in 2014 in Zhejiang. Conclusion The pathogen causing the viral meningitis outbreak in Dongtou in 2015 was ECHO30 genotype Ⅰ.