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[Characterization of enterovirus type 71 isolated in Saitama Prefecture in 2000]
M Shinohara1, K Uchida, S Shimada
1Saitama Institute of Public Health.
Abstract:
Coxsackievirus A16 (CA16) has been isolated mainly from hand, foot and mouth disease patients for the past several years in Saitama Prefecture, Japan, but in 2000, enterovirus 71 (EV71) was isolated with high frequency. Also, many cases with aseptic meningitis were reported unusually. We determined partial nucleotide sequences of EV71 isolated in this year and compared them with those of the viruses isolated previously. Eighteen strains of EV71 were isolated from May to September in 2000. The sequence analysis of about 700 nucleotides between 5' NCR and VP2 region indicated that the EV71 strains isolated in Saitama Pref. in 2000 were classified into three groups. The first group was consisted of the strains which showed 89 to 91% nucleotide similarity with TW/2086/98, NCKU 9822 isolated in Taiwan and strain SA/448/99 isolated in Saitama Pref. in 1999. The second group was highly similar to both Taiwan strains and SA/448/99 (92 to 93% nucleotide similarity). The first and second groups were also considered to be subgroups belonging to the same group. And the third group was highly similar to 18/Sin/97, 13/Sin/98 isolated in Singapore. These viruses were genetically close to MS7423/87, which has shown neurovirulence. Furthermore, from geographical origin of specimens, we found that the Taiwan like strains were isolated in the west area (Kawagoe, Tokorozawa) and Singapore like strains were isolated in the south area (Urawa, Kawaguchi, Toda). Also, almost every EV71 strains isolated from the patient with aseptic meningitis were close to Singapore strains. It was found that EV71 strains isolated in 2000 were different from the strains isolated past in Saitama Pref. and some of them were close to the neurovirulent strain.
Insights
In 2000, Enterovirus 71 (EV71) emerged in Saitama, Japan, causing aseptic meningitis. Genetic analysis revealed three distinct EV71 groups, some linked to neurovirulent strains and specific geographic origins.
Area of Science:
- Virology
- Molecular Epidemiology
- Public Health
Background:
- Coxsackievirus A16 (CA16) was previously dominant in hand, foot, and mouth disease cases in Saitama Prefecture, Japan.
- Unusual increases in aseptic meningitis cases were reported in Saitama in 2000.
- Enterovirus 71 (EV71) isolation frequency significantly increased in Saitama during 2000.
Purpose of the Study:
- To genetically characterize Enterovirus 71 (EV71) strains isolated in Saitama Prefecture in 2000.
- To compare the genetic profiles of these EV71 strains with previously isolated strains and international strains.
- To investigate potential correlations between EV71 genetic groups, geographical distribution, and clinical manifestations like aseptic meningitis.
Main Methods:
- Isolation of 18 EV71 strains from patients between May and September 2000.
- Partial nucleotide sequencing of approximately 700 bases (5' NCR to VP2 region).
- Phylogenetic analysis to determine nucleotide similarities and relationships with reference strains from Taiwan, Singapore, and previous Saitama isolates.
Main Results:
- EV71 strains from 2000 clustered into three distinct genetic groups based on nucleotide sequence analysis.
- Group 1 and 2 strains showed high similarity (89-93%) to Taiwan and 1999 Saitama isolates, considered subgroups of the same lineage.
- Group 3 strains exhibited high similarity to Singapore isolates and were genetically close to a known neurovirulent strain (MS7423/87).
- Taiwan-like strains were found in western Saitama, while Singapore-like strains predominated in southern areas.
- EV71 strains associated with aseptic meningitis were predominantly of the Singapore-like genetic type.
Conclusions:
- EV71 strains circulating in Saitama in 2000 were genetically distinct from those previously identified in the region.
- The emergence of EV71 strains, particularly those related to neurovirulent lineages, poses a significant public health concern.
- Geographic clustering of EV71 strains suggests localized transmission dynamics.
- The association of specific EV71 genetic groups with aseptic meningitis warrants further investigation into virulence factors and disease pathogenesis.