A conventional PCR-based method to detect the E2 gene of the rubella virus for epidemiological analysis.

To eliminate the rubella virus (RV), genetic characterization is vital for its detection, identification of endemic transmission, and diagnosis of imported cases. The 739-nucleotide region in the E1 gene has primarily been used for genotyping for epidemiological analysis. However, in the 2018-2019 RV outbreak, identical sequences were observed in patients who were not epidemiologically linked. Additionally, the 739 nt sequences from the outbreak in Tokyo in 2018-2019 were identical to RV identified in China in 2019. This suggests that this region may be insufficient to identify the detected RV strains as endemic or imported. In 62.4% of the specimens, the E1 gene sequences of the 1E RV genotype were identical. Additionally, the observed discordance of sequences from the mainly detected identical sequence in the 739-nt sequence of the E1 gene were one (31.0%), two (3.5%), three (2.6%), and four (0.23%). Moreover, a comparison of the complete structural protein-coding region suggests that the E2 gene is more diverse than the E1 and the capsid gene. Thus, conventional polymerase chain reaction (PCR) primers were developed to detect the E2 gene and improve epidemiological analysis. A comparison of the sequences identified during the RV outbreak in Tokyo revealed genetic differences in the sequences (15 of the 18 specimens). These results suggest that additional information could be obtained by simultaneously analyzing the E2 and the E1 region. The identified sequences can potentially aid in evaluating the RV strains detected during epidemiological analysis.