{
  "abstract": "Background: Leptospirosis causes approximately 1.03 million cases and 58,900 deaths annually worldwide yet remains underrecognized because infections are often mild or self-limiting and require serological confirmation. In Bhutan, limited diagnostic capacity constrains surveillance, and data on human exposure in high-risk subtropical areas are limited. This study aimed to estimate seroprevalence, identify circulating serovars, map geographic distribution of seropositive cases, and assess potential risk factors for Leptospira exposure among adults in subtropical Bhutan. Methods/principal findings: We conducted a cross-sectional study during September–October 2024 in six subtropical communities in southern Bhutan. A total of 503 adults were enrolled using probability-proportional-to-size (PPS) sampling; 492 were included in the final analysis after excluding 11 participants for inadequate blood sample or hemolysis. Serum samples were tested by IgM and IgG ELISA and by microscopic agglutination test (MAT), the reference standard used to define seropositivity for potential risk factor analysis and primary reacting serovar identification. MAT-based seroprevalence was 19.3% (95% CI: 16.0 – 23.1), compared with 22.4% (95% CI: 18.8 – 26.4) by ELISA IgM and 16.1% (95% CI: 13.0 – 19.7) by ELISA IgG. Among MAT-positive samples (n = 95), the predominant serovars were Australis (49%) and Lai-like (13%). Gelephu Thromde had the highest serovar diversity, while Australis and Patoc were detected in all six study areas. Multivariable logistic regression identified paddy farming (adjusted OR: 4.74; p < 0.001) and drinking unboiled water (adjusted OR: 2.34; p = 0.002) as independently associated with MAT seropositivity. In addition, residence in crowded urban (adjusted OR: 4.08; p = 0.001) or urban areas (adjusted OR: 2.94; p = 0.002) relative to rural areas and lower education (primary education: adjusted OR: 2.52; p = 0.013; unable to read and write: adjusted OR: 2.02; p = 0.034) were associated with MAT seropositivity. Conclusion/significance: Approximately one in five adults in subtropical Bhutan had serological evidence of prior Leptospira spp. exposure, indicating that human exposure is more common than previously recognized. Given the cross-sectional design, these associations cannot establish temporality and self-reported exposure to potential risk factors may be subject to recall bias. These findings, however, provide baseline data on population exposure and point to actionable public health interventions: (1) educate communities on preventive behaviors, (2) promote use of protective gear during high-risk activities, (3) expand research and surveillance capacity to better understand the epidemiology of leptospirosis and (4) strengthen hospital-based diagnostics to enable early treatment and reduce complications from leptospirosis in Bhutan. Author summary: Leptospirosis is a zoonotic disease caused by Leptospira spp. The bacteria are harbored by a wide range of mammals, particularly rodents. It remains an under-recognized public health challenge in the subtropical region of Bhutan. This study investigated seroprevalence and associated potential risk factors in six communities in subtropical Bhutan. We found that 19.3% of participants were seropositive for Leptospira antibodies, indicating that approximately one in five people had evidence of prior exposure. Among the potential risk factors, people engaged in paddy farming and those who reported drinking unboiled water in 12 months preceding the study had higher odds of being seropositive. These findings should inform public health interventions, including educating communities on preventive behaviors, promoting use of protective gear during high-risk activities and expanding research and surveillance capacity for leptospirosis in Bhutan.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Global Health and Infectious Diseases, Graduate School of Public Health, International University of Health and Welfare, Narita, Japan",
    "Health and Medical Research Centre, Central Regional Referral Hospital, Gelephu, Bhutan",
    "Department of Internal Medicine, Central Regional Referral Hospital, Gelephu, Bhutan",
    "Department of Pharmacy, Central Regional Referral Hospital, Gelephu, Bhutan",
    "Faculty of Postgraduate Medicine, Khesar Gyalpo University of Medical Sciences of Bhutan, Thimphu, Bhutan",
    "Department of Pathology and Laboratory Medicine, Jigme Dorji Wangchuck National Referral Hospital, Thimphu, Bhutan",
    "Department of Laboratory Medicine, Central Regional Referral Hospital, Gelephu, Bhutan",
    "Ministry of Health, Royal Government of Bhutan, Thimphu, Bhutan",
    "Royal Centers for Disease Control, Thimphu, Bhutan",
    "Department of Clinical Nursing, Central Regional Referral Hospital, Gelephu, Bhutan",
    "Department of Infectious Diseases, School of Medicine, International University of Health and Welfare, Narita, Japan"
  ],
  "article_type": "Research Article",
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  "author_total": 14,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Monu Tamang",
      "orcid": "0000-0003-1198-5856"
    },
    {
      "affs": [
        0
      ],
      "name": "Rie Takeuchi"
    },
    {
      "affs": [
        1,
        2
      ],
      "name": "Thinley Dorji",
      "orcid": "0000-0003-4932-8704"
    },
    {
      "affs": [
        1,
        3
      ],
      "name": "Kinley Choki"
    },
    {
      "affs": [
        4,
        5
      ],
      "name": "Tshokey Tshokey"
    },
    {
      "affs": [
        6
      ],
      "name": "Chenga Dawa"
    },
    {
      "affs": [
        7
      ],
      "name": "Choki Dolkar"
    },
    {
      "affs": [
        8
      ],
      "name": "Kesang Wangchuk"
    },
    {
      "affs": [
        8
      ],
      "name": "Dorji Tshering"
    },
    {
      "affs": [
        1,
        9
      ],
      "name": "Sangay Tenzin"
    },
    {
      "affs": [
        6
      ],
      "name": "Kinley Wangchuk"
    },
    {
      "affs": [
        8
      ],
      "name": "Rinzin Wangchuk"
    },
    {
      "affs": [
        0
      ],
      "name": "Naoko Yamamoto"
    },
    {
      "affs": [
        10
      ],
      "name": "Yasuyuki Kato"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/41basc2fq52b9.bib",
  "cited_by": 0,
  "doi": "10.1371/journal.pntd.0014821",
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  "native_subjects": [
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  "pmcid": "PMC13734453",
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  "published": "2026-11-04",
  "publisher": "Public Library of Science",
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  "title": "Seroepidemiology of human leptospirosis in subtropical Bhutan, 2024",
  "title_text": "Seroepidemiology of human leptospirosis in subtropical Bhutan, 2024",
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