Characterization of enterovirus type 71 isolated in Saitama Prefecture in 2000

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.