Work

An emerging tick-borne spotted fever group Rickettsia in China: Isolation, genomics, and human infection of Rickettsia koreansis

Year: 2026

Type: article

Abstract: OBJECTIVES: This study aimed to isolate and systematically characterize the emerging Rickettsia koreansis from ticks in China, define its genomic features, and assess its clinical and epidemiological significance for human health. METHODS: Rickettsiae were isolated from larval Rhipicephalus microplus ticks by cell culture and biologically characterized. Whole-genome sequencing and assembly were performed for phylogenetic analysis. Comparative genomics was used to identify functional features. Human infections were confirmed by pathogen-specific PCR and serological assays, and clinical characteristics were described. Infection prevalence and distribution of ticks were determined. RESULTS: A novel isolate, designated R. koreansis str. TIGMIC YN, was successfully obtained. It exhibited an average nucleotide identity of 99.93% and a digital DNA-DNA hybridization value of 98.1% with the Korean reference strain CNH17-7, indicating that they belong to the same species. Synteny and pangenome analyses revealed that despite extensive structural conservation, TIGMIC YN displays distinctive strain-level adaptation through localized chromosomal rearrangements and unique gene clusters. Through sentinel surveillance, eight laboratory-confirmed human infections were identified, all presenting with mild febrile illness or other nonspecific symptoms. Among 554 tick samples, R. koreansis was detected in seven tick species, with an overall infection rate of 27.4%, across ten provinces or autonomous regions in China. CONCLUSION: R. koreansis's broad vector range, defined genomic features, and demonstrated human infectivity underscore the need to strengthen epidemiological surveillance, develop specific diagnostic tools, and improve clinical recognition of infections caused by this pathogen.

Source: Journal of Infection

DOI: 10.1016/j.jinf.2026.106729