[Epidemiological and molecular traceability analysis of the first cluster outbreak of D8 genotype measles in Henan Province].

In February 2025, a local cluster outbreak caused by the D8 genotype Measles virus (MV) was first discovered in Henan Province. Epidemiological investigations and laboratory testing were conducted, including the collection of serum and throat swabs for MV IgM antibody and nucleic acid detection, virus isolation and genetic homology analysis. Measures such as close contact tracing, vaccination rate assessment and supplementary immunization activities were implemented, successfully preventing broader community transmission. A total of three cases were reported during the outbreak, including one imported-related adolescent and two secondary local adult cases. All cases presented with typical symptoms such as fever and rash. Both adult cases were complicated by pneumonia, with one case developing into severe pneumonia. MV genotyping showed that the two secondary cases were both the D8 genotype, with the viral sequences being completely homologous to the Kazakhstan strain. Among the close contacts, 98.2% were adults, and 142 individuals received emergency vaccination.