A population-based serosurvey of 1,194 adults across 74 villages in Chiang Rai province, Thailand (2023) found IgG seropositivity against Orientia tsutsugamushi—the bacterium causing scrub typhus—at 60% among highland ethnic minority populations versus just 13% among lowland Thai participants, a nearly five-fold disparity. Forest and agroforestry exposures predicted seropositivity in Thai participants (aOR 2.87 and 1.74, respectively), but these classical environmental risk factors failed to explain the dramatically elevated burden in highland communities, where significant village-level heterogeneity persisted even after full adjustment.
Scrub typhus kills an estimated one million people annually across the Asia-Pacific and remains severely underdiagnosed due to nonspecific fever presentation and limited laboratory infrastructure. This preprint—not yet peer-reviewed—adds important granularity to that burden picture. The finding that conventional risk pathways (forest exposure, domestic contact, individual prevention behaviors) don't adequately account for highland risk is genuinely consequential: it suggests unmapped transmission routes—possibly peridomestic chigger mite habitats, livestock interfaces, or housing structure differences—that current public health messaging entirely misses. The two-stage random sampling and Luminex xMAP platform strengthen methodological credibility, though cross-sectional design precludes causal inference. Critically, the 60% seroprevalence implies widespread subclinical infection, raising questions about cumulative immune protection versus reinfection risk. For highland communities in northern Thailand and analogous marginalized populations across Southeast Asia, targeted surveillance redesign is warranted rather than scaled-up generic prevention campaigns.