Identification of the first C1 subgenotype of enterovirus 71 in the Chinese mainland in a retrospective study.

The C4 sub-genotype of Enterovirus 71 (EV71) has been identified as the most dominant sub-genotype circulating in the Chinese mainland since 1998. The circulation situation of EV71 before 1998 is not well established due to insufficient experimental data. The C1 subgenotype of EV71 has not yet been reported in the Chinese mainland by now. Based on the AFP surveillance system of the mainland of China, this study conducted a retrospective study of AFP cases for 1985-1999: a strain of EV-A71 C1 subgenotype was found. To our knowledge, this strain (SD92-41) is the first C1 sub-genotype reported in the Chinese mainland. This study demonstrates that the C1 gene subtype also appeared in the Chinese mainland, but it is unknown whether it is an imported or a local epidemic strain. With sufficient information known from retrospective studies, the source of the SD92-41 strain will be identified and the prevalence of EV-A71 in the Chinese mainland before 1998 will be clearer.