Why the study?
Scrub typhus is a re-emerging public health concern, but prevention strategies remain inadequate on Hainan Island, China, where it poses a significant threat.
Observational (n=156)
Yes
High genetic diversity of Orientia tsutsugamushi was observed across Hainan Island, with specific sub-genotypes showing distinct pathogen density trends during infection.
Heightened Hainan surveillance for diverse Orientia strains warranted; leaves open avian role in long-distance transmission.
BACKGROUND: Scrub typhus, traditionally caused by Orientia tsutsugamushi, is a re-emerging public health concern within the Tsutsugamushi Triangle. Despite growing awareness, prevention strategies remain inadequate on Hainan Island, China, where scrub typhus poses a significant threat, especially in field-related environments. METHODOLOGY/PRINCIPAL FINDINGS: Gene flow analysis of the tsa56 gene and multilocus sequence typing (MLST) were conducted on 156 previously confirmed scrub typhus cases from 2018 to 2021 across Hainan Island. By integrating published datasets, we identified 12 major sub-genotypes and traced their origins, revealing that these sub-genotypes share origins with isolates from Southeast Asia and coastal provinces and island of China, but also demonstrate unique local adaptations across all isolates. Alpha diversity index analysis was applied across administrative regions to identify hotspot regions. This analysis showed that nine out of the detected fourteen administrative regions, particularly along the northern and western coastlines and inland areas, exhibited relatively high genetic diversity, with the highest incidence observed in Qiongzhong, a centrally located city. Related major sequence types were mapped, and distances between locations were estimated, showing that identical MLST sequence types were observed to transfer across distances of 23 to 125 km between different sites on the island. Pathogen density was analyzed using quantitative real-time PCR targeting the tsa56 gene. Without accounting for potential confounding factors or dataset limitations, the Karp_B_2 sub-genotype showed a significant increasing trend in pathogen density with prolonged fever duration, while Gilliam sub-genotypes exhibited a slower or even declining trend. CONCLUSIONS/SIGNIFICANCE: These findings emphasize the urgent need for targeted public health interventions, particularly focusing on vulnerable populations in rural and agricultural areas of nine key administrative regions where high genetic diversity and pathogen spread were observed. Additionally, this study provides valuable insights into the transmission dynamics and infection progression of scrub typhus, using gene flow analysis and multilocus sequence typing to identify major sub-genotypes.
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Tang et al. (2025) conducted an observational in Scrub typhus (n=156). Orientia tsutsugamushi sub-genotypes (e.g., Karp_B_2) vs. Other sub-genotypes (e.g., Gilliam) was evaluated on Pathogen density trend with prolonged fever duration.
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