Epidemiological Features and Evolutionary Analysis of Recombinant CVA24v in the Context of a Re-Emerging AHC Outbreak in China, 2023.

China experienced another outbreak of acute hemorrhagic conjunctivitis (AHC) in 2023, with a total of 195 297 recorded cases. This marks the third nationwide outbreak in nearly two decades, following previous outbreaks in 2007 and 2010. Descriptive epidemiological analysis shows that the number of cases in 2023 peaked in September, similar to the last two outbreaks. The age groups with the highest incidence rate of the three outbreaks in 2007, 2010, and 2023 are 15-20, 10-15, and 10-15 years old, respectively. Students are the main occupational group in the three outbreaks. Hainan, Guangxi, and Guangdong were the top three regions with high incidence rates in the three outbreaks. In 2023, the incidence rate in Hainan Province is the highest ever. Pathogenetic analyses show that the pathogens isolated during the 2023 outbreak were identified as the GIV genotype of CVA24v. Seven different recombination patterns were identified in the recombination analysis of the Chinese strains in 2023 and representative strains of global outbreaks since 1988. These patterns mainly involved the recombination signals of EV-C96 and PV in the 5' untranslated region and 3C and 3D regions. Although recombination events of CVA24v are rarely reported, its recombination was consistently present through systematic analysis in this study. This study comprehensively analyzed the 2023 AHC re-emerging data and isolated CVA24v sequences, providing valuable data for future CVA24v molecular epidemiology studies.