Seroprevalence of Burkholderia Pseudomallei among International Travellers

OBJECTIVES:Melioidosis, caused by Burkholderia pseudomallei, is increasingly recognised as a travel-associated infection, yet the extent of exposure among international travellers remains unknown. We aimed to determine B. pseudomallei seroprevalence among travellers to Southeast Asia and explore risk factors. METHODS:We conducted a cross-sectional study at the Hospital for Tropical Diseases, Bangkok, enrolling travellers aged ≥18 years from non-endemic regions who had spent ≥1 month in Southeast Asia. Sera were tested by indirect ELISA using two B. pseudomallei antigens, Hcp1 and O-polysaccharide (OPS). Predefined diagnostic and exposure serological thresholds were applied. Risk factors were assessed by logistic regression. RESULTS:Between August 2025 and January 2026, 370 travellers were enrolled. Overall, 49 (13.2%) were seropositive, including 25 (6.8%) with probable melioidosis and 24 (6.5%) with probable environmental exposure. Independent risk factors were female sex (aOR 2.49; 95% CI 1.06-5.83), North American origin (aOR 2.78; 1.17-6.59), and underlying medical conditions (aOR 3.28; 1.39-7.75). CONCLUSION:B. pseudomallei exposure among travellers to Southeast Asia is not rare, with one in eight seropositive. Inclusion of melioidosis in the differential diagnosis of febrile returning travellers, complemented by diagnostic approaches beyond culture alone, is needed to reduce misdiagnosis and preventable mortality.