Melioidosis

Melioidosis is an infectious disease caused by Burkholderia pseudomallei, a gram-negative, motile, saprophytic bacterium that functions as an opportunistic facultative intracellular pathogen. The organism is oxidase-positive and exhibits a characteristic 'safety pin' appearance on Gram stain due to a central granule. B. pseudomallei produces a glycocalyx polysaccharide capsule that contributes to its resistance against various antibiotics. The bacteria emit a strong soil odor after 24 to 48 hours of growth in culture, though this is not recommended as a routine identification method.

The clinical presentation of melioidosis is highly variable, earning it the nickname 'the great mimicker' due to non-specific signs and symptoms. Most exposed individuals remain asymptomatic; however, symptomatic disease can progress rapidly to sepsis with fever, with or without pneumonia, localized abscesses, or other focal infections. The mean incubation period is 9 days, with a range of 1 to 21 days, though symptoms may manifest within 24 hours following near-drowning events. Approximately 10% of patients develop chronic melioidosis, defined by symptoms persisting longer than two months, presenting with fever, weight loss, productive cough potentially mimicking tuberculosis, and multiple abscesses at various body sites. Complications include pneumonia, abscess formation, and septic shock, which can be fatal. Diabetes mellitus represents one of the most important risk factors for developing symptomatic disease.

Melioidosis is endemic throughout Southeast Asia, particularly in northeast Thailand, and in northern Australia. The infection is constantly present in these regions, with environmental contamination of soil and surface water serving as the primary reservoir. Prior to the Vietnam War, fewer than a handful of cases had been diagnosed in the United States during the twentieth century. Following the conflict, the phenomenon termed the 'Vietnam time-bomb' emerged, documenting delayed onset pulmonary infections in servicemen previously deployed in Vietnam, with estimates suggesting up to 250,000 U.S. soldiers were potentially exposed. Latent infections have been documented for periods up to 29 years, though one controversial report suggested a 62-year latency period in a prisoner of war. The disease burden in temperate countries such as Europe and the United States remains to be fully characterized in the available source material.

Human infection occurs through direct contact with contaminated soil or surface water, with B. pseudomallei entering the body through wounds, inhalation, or ingestion. The bacterium is most abundant at soil depths of 10 to 90 centimeters and has been isolated from soils, ponds, streams, pools, stagnant water, and rice paddy fields. B. pseudomallei demonstrates remarkable environmental persistence, surviving for more than 16 years in nutrient-poor conditions including distilled water, desert soil, and nutrient-depleted soil. The organism resists antiseptic and detergent solutions and acidic environments (pH 4.5 for 70 days), with optimal growth at temperatures ranging from 24°C to 32°C. Ultraviolet light is lethal to the bacteria. Person-to-person or animal-to-human transmission is extremely rare.

Individuals with diabetes mellitus face significantly elevated risk for developing symptomatic melioidosis. Persons with recent exposure to endemic areas through travel, military service, or occupational contact with soil and water face increased exposure risk. Near-drowning victims in contaminated water represent a high-risk group for rapid-onset disease. The potential for prolonged latency lasting decades necessitates consideration of melioidosis in patients with compatible symptoms and any history of exposure to endemic regions, even if exposure occurred many years previously.

Source-backed detail is not yet available for prevention measures.

Source-backed detail is not yet available for surveillance methodology.

1. 1 Wikidata. melioidosis.
2. 2 Wikipedia. Melioidosis - Wikipedia.

ICD-10

ICD-11

Total cases

4

Peak month

2025-08

Coverage

2 reporting countries · 2012-09-14 → 2026-05-09