An Imported Yellow Fever Adverse Events Following Immunization Case Identified by Targeted Next-Generation Sequencing - Guangdong Province, China, October 2024.

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Yellow fever (YF) is a highly lethal mosquito-borne infectious disease endemic to tropical regions for which no antiviral treatments currently exist. Vaccination remains the most effective preventive measure and is recommended by the World Health Organization (WHO) for YF control and prevention. However, the YF vaccination associated Adverse Events following Immunization (AEFI) cases occur globally occasionally. This report describes the first imported suspected YF case in China in 2024, which was a 46-year-old Peruvian man with a recent YF vaccination history. Guangdong CDC employed Targeted Next-Generation Sequencing (tNGS) analysis to determine whether the patient was infected by the wild-type YF virus strain or experienced an AEFI. tNGS analysis successfully yielded a 10.2 kb viral genomic sequence and BLAST analysis revealed high similarity to the YF vaccine strain 17D-213. Phylogenetic analysis classified the sequence within the West Africa II genotype, clustering with the 17D vaccine strain and showing 99.89%-99.79% homology with vaccine strains, while demonstrating only 85.4%-84.9% similarity to wild-type YF virus strains from South America. Based on this evidence, an expert panel consultation concluded that this case represented YF AEFI. The implementation of tNGS technology enables more precise and expeditious pathogen sequencing, providing critical evidence for accurate disease diagnosis and informed public health interventions.