Molecular identification of enteroviruses including two new types (EV-98 and EV-107) isolated from Japanese travellers from Asian countries

Of 58 enterovirus strains isolated from Japanese travellers returning from Asian countries, eight were non-serotypable with existing antisera. By sequencing a part of the VP1 region, six of these strains were typed as echovirus 9, enterovirus (EV)-73, EV-79 or EV-97. The nucleotide identity of the VP1 region of isolate T92-1499 to all enterovirus prototypes was <70 %. The VP1 sequence of isolate TN94-0349 was closely related to coxsackievirus (CV)-A9 (73.3 % nucleotide identity), but the virus could not be neutralized with a serum raised against the prototype CV-A9 strain. On the basis of complete molecular comparisons, T92-1499 and TN94-0349 were identified as EV-98 and EV-107, respectively, by the ICTV Picornavirus Study Group. Serum neutralization tests of Japanese individuals revealed a seroprevalence rate of 11 % for EV-73, and even lower seroprevalence rates, 1.0-3.8 %, were found for the other new enteroviruses, suggesting that prior circulation of these viruses in Japan was unlikely.