To estimate Burkholderia pseudomallei antibody seroprevalence among international travelers to Southeast Asia and identify factors associated with seropositivity.
Approach:
Study Design: A single-center, cross-sectional study was conducted at the Hospital for Tropical Diseases in Bangkok, Thailand, from August 1, 2025, through March 31, 2026. Participants were enrolled between August 2025 and January 2026.
Participants: The study included 370 travelers aged 18 years or older from nonendemic regions who had spent at least one month in Southeast Asia.
Procedures: Participants completed questionnaires about travel, environmental exposures, and medical history. Blood samples were tested for antibodies to two B. pseudomallei antigens using enzyme-linked immunosorbent assays.
Statistical Analysis: Researchers applied separate antibody thresholds for probable melioidosis and probable environmental exposure, then used logistic regression to assess factors associated with seropositivity. The 38% prevalence estimate was used to plan the sample size; it was not the observed result.
Key Findings:
Forty-nine of 370 travelers (13.2%) were seropositive: 25 (6.8%) met the higher threshold for probable melioidosis, and 24 (6.5%) met the threshold for probable environmental exposure. These are serological classifications, not confirmed clinical diagnoses.
Female sex, North American origin, and at least one underlying medical condition were independently associated with seropositivity.
All seropositive participants were clinically healthy when tested.
Interpretation:
Approximately one in eight travelers met a study threshold for seropositivity. A positive result provides serological evidence of possible exposure, but it cannot establish when exposure occurred, confirm clinical infection, or show whether viable bacteria remain.
Limitations:
The single-center, cross-sectional design limits generalizability and cannot determine whether antibodies arose during the current trip or an earlier exposure.
Travel exposures were self-reported. The O-polysaccharide assay may cross-react with other environmental Burkholderia species, potentially inflating the estimated B. pseudomallei-specific seroprevalence.
Conclusion:
The findings support considering melioidosis in the differential diagnosis of febrile returning travelers. The clinical significance of seropositivity in travelers who feel well and the role of post-travel antibody screening require further study.
