Incidence of Meliodosis
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melioidosis incidence epidemiology
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melioidosis global incidence epidemiology 2024 2025
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https://www.mdpi.com/2076-0817/13/11/926
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Here is a consolidated overview of the incidence of melioidosis:
Melioidosis - Incidence and Epidemiology
Causative Organism
Melioidosis is caused by Burkholderia pseudomallei (formerly Pseudomonas pseudomallei), a motile, pleomorphic, Gram-negative aerobic bacillus. It is a natural saprophyte found in freshwater and damp soil in the humid tropics. - Goldman-Cecil Medicine, p. 1159
Global Burden
| Metric | Estimate |
|---|---|
| Annual cases (worldwide) | ~165,000 (95% CI: 68,000-412,000) |
| Annual deaths | ~89,000 (95% CI: 36,000-227,000) |
| Endemic countries (confirmed) | At least 45 |
| Likely endemic (unconfirmed) | 34 additional countries |
These figures come from the landmark Limmathurotsakul et al. (2016) modeling study in Nature Microbiology. Melioidosis is considered severely underreported globally due to limited laboratory capacity.
Endemic Regions and Regional Incidence
Highest burden areas:
- Southeast Asia - especially northeastern Thailand and Singapore (incidence ~50/100,000 population in endemic zones)
- Northern Australia - particularly the Northern Territory (case-fatality rate 6-23%)
- Indian subcontinent and Sri Lanka
Additional regions reporting cases:
- Africa (several countries now recognized as likely endemic)
- Mexico and northern South America
- Madagascar
Expanding geographic range (2024 updates):
- Recent 2024 narrative review in Pathogens confirms melioidosis is endemic in over 45 countries, with newly documented locally acquired cases in the Southern United States (including Mississippi, Puerto Rico, and the US Virgin Islands). Hurricane Helene (September 2024) was linked to cases in Georgia.
- Climate change and flooding are driving further geographic expansion.
Demographic and Seasonal Patterns
- Seasonality: Peak incidence during rainy monsoon seasons; >75% of cases occur in the local wet season - Fitzpatrick's Dermatology, p. 3868
- Occupational risk: In Thailand, most common in rice farmers; male-to-female ratio 4:1 due to occupational exposure
- Seroprevalence: In endemic rural Thailand, 5-20% of inhabitants have antibodies, indicating prior mostly asymptomatic infection
Risk Factors for Clinical Disease
- Diabetes mellitus (most common - present in ~50% of cases)
- Chronic renal disease
- Heavy alcohol consumption
- Chronic respiratory disease
- Thalassemia
- Glucocorticoid therapy / immunosuppression
- Cancer
- Underlying malignancies (~10% of cases) and immunosuppressive therapy (~9%)
Note: Patients without identified risk factors do not have a decreased risk of death - Goldman-Cecil Medicine, p. 1159
Routes of Transmission
- Primary: Percutaneous inoculation via contact of open skin with contaminated soil or water
- Inhalation of contaminated droplets, soil, or dust
- Gastrointestinal route (less common)
- HIV infection does not appear to increase risk or severity
Travel-Associated Cases
A 2025 systematic review (PMID: 41595830) documented over 200 cases of travel-associated melioidosis in non-endemic regions, with diagnostic delays of up to 18 months reported. About a dozen cases are identified annually in the US, mostly in returning travelers.
Key Takeaway on Underreporting
Melioidosis is widely considered the "tip of the iceberg" - most endemic countries lack the microbiological infrastructure to culture-confirm cases, meaning real-world incidence is likely far higher than reported figures. The 165,000 annual case estimate itself carries wide uncertainty bounds.
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