Melioidosis in South Asia: The hidden endemicity we can no longer ignore

Melioidosis, caused by Burkholderia pseudomallei, remains one of the most overlooked tropical infections—deadly, yet curable. Despite its discovery more than a century ago, this disease continues to hide behind the masks of tuberculosis, pneumonia, or sepsis, killing silently in regions where it is least recognized. In 2016, modelling studies estimated that South Asia accounts for nearly 44% of the global burden of melioidosis. (Limmathurotsakul et al., 2016) Yet only a handful of countries—India, Sri Lanka, and Bangladesh—routinely diagnose and report human cases. In contrast, neighbouring nations such as Pakistan, Nepal, Bhutan, and Afghanistan have scarcely detected any cases, not because the disease is absent, but because it remains unseen — buried beneath diagnostic inexperience, limited laboratory capacity, and low clinical suspicion.

The paradox is striking - while these countries share similar climatic, agricultural, and socioeconomic profiles, the ability to detect B. pseudomallei varies drastically. The challenge is not the complexity of the organism but the simplicity of its neglect. In much of South Asia, clinicians have little exposure to the disease’s protean manifestations, and microbiology laboratories often lack the tools or protocols to identify B. pseudomallei, which is easily mistaken for common contaminants. In standard medical textbooks, melioidosis receives barely a paragraph—an invisibility that perpetuates its underdiagnosis.

Rising awareness: A shift in India and Bangladesh

There is, however, a quiet transformation underway. In India, the establishment of a national task force to strengthen laboratory capacity across 14 states has changed the landscape dramatically. Through systematic awareness and capacity-building initiatives, case detection has increased nearly tenfold in just two years. Similarly, in Bangladesh, structured efforts such as the four-day Melioidosis Workshop in 2021 and the 3rd South Asian Melioidosis Congress in Dhaka (2023) have led to better recognition, early diagnosis, and improved clinical outcomes. (Muhib et al., 2025) These examples demonstrate that awareness and training—not technology alone—can alter the trajectory of melioidosis in South Asia.

Seroprevalence: the hidden footprint of exposure

The number of diagnosed cases often mirrors the seroprevalence of the disease—an indirect marker of human exposure to B. pseudomallei. Studies from Karnataka (Vandana et al., 2016) and Odisha (Behera et al., 2025) from India and from Bangladesh (Jilani et al., 2016) reveal how seroepidemiology uncovers the invisible burden of this infection. In the eastern coastal region of India, a 20.9% seroprevalence (410/1920) was reported, suggesting widespread environmental exposure, especially in rural communities. This reflects the silent interface between humans, soil, and water where B. pseudomallei thrives.

Seasonally, Indian case series show that more than half of the infections (52.1%) occur during the monsoon, followed by the post-monsoon (25%), winter (11.8%), and pre-monsoon (11.1%) periods. (Sarin et al., 2025) High rainfall, moist soil, and moderate temperatures provide optimal conditions for bacterial persistence and transmission. Spatial risk mapping in Odisha has identified Cuttack, Balasore, Khordha, and Jajpur districts as hotspots—regions where environmental exposure coincides with dense human habitation. Such clustering underscores the need for region-specific surveillance. Asymptomatic seropositivity, therefore, is not a trivial finding—it is a powerful epidemiological tool to predict outbreak potential, guide early diagnosis, and shape targeted public health responses. (Vandana et al., 2016)

A growing but hidden burden

What we see today may represent only the tip of the iceberg. In northern India, where clinical suspicion remains low, sporadic case reports suggest an emerging pattern. The convergence of rising diabetes prevalence, climate variability, and rural exposure portends a widening endemic footprint. Yet, the major challenges remain: lack of clinical awareness, overlapping symptoms with tuberculosis or bacterial pneumonias caused by other pathogens, non-specific imaging findings, and insufficient diagnostic infrastructure.

The role of climate and environment

The interplay between climate, environment, and disease has long been recognized in melioidosis but remains largely underexplored in South Asia. Studies worldwide have shown that rainfall, soil moisture, groundwater levels, temperature, dew point, and cloud cover are key determinants of disease occurrence. Rainfall raises soil water tables, mobilizing B. pseudomallei toward the surface, while reduced solar radiation and cloud cover increase bacterial survival by limiting UV exposure. Extreme weather events—floods and cyclones—further disperse the pathogen into human habitats, heightening the risk of infection. These environmental determinants, if mapped and modelled, could serve as early warning systems for melioidosis outbreaks. (Kenyon, 2024)

Clinical challenges: the great masquerade

Melioidosis is the “great imitator.” Abscesses caused by B. pseudomallei often mimic tuberculosis, fungal infections, or more common bacterial infections caused for example by Staphylococcus aureus or Klebsiella pneumoniae. Clinical scoring systems, though imperfect, can aid early suspicion. Recent studies have identified a “tri-low” hematological pattern—low total leukocyte count (TLC<7900/µL), absolute neutrophil count (ANC<5245/µL), and absolute lymphocyte count (ALC<615/µL)—as a predictor of severe disease and poor outcomes, likely reflecting immune exhaustion. (Gupta et al., 2024)

Imaging plays a key role in identifying deep-seated abscesses; radiological findings such as honeycombing, multifocal abscesses, or cavitary lesions can guide early suspicion. Crucially, the management of melioidosis-associated abscesses requires an intensive antimicrobial phase with meropenem or ceftazidime, followed by an eradication phase with cotrimoxazole. Surgical drainage—mandatory for prostatic abscesses and considered judiciously for other sites — can significantly enhance antibiotic penetration and improve clinical outcomes, especially in deep or refractory collections. (Gupta et al., 2025)

Diagnostics: the need for speed and accessibility

“Early diagnosis is not academic—it saves lives.” Yet, the greatest bottleneck in melioidosis management is delayed microbiological confirmation. If culture facilities are available, this diagnostic limitation can be mitigated by assessing suspicious isolates using a simple algorithm including the distinctive antibiotic resistance profile of B. pseudomallei, which is feasible even in resource-limited microbiology laboratories. (Bhattarai et al., 2024) Blood culture remains the diagnostic gold standard, but many patients with localized disease have negative blood cultures, requiring invasive sampling of pus or tissue. The absence of a rapid point-of-care test is a major gap, especially in peripheral and emergency settings. Encouraging progress has been made in identifying B. pseudomallei-specific antigens and translating these findings into serological point-of-care assay, (Wagner et al., 2020) although their true clinical performance still needs to be determined in prospective studies.

Innovations such as loop-mediated isothermal amplification (LAMP) are now showing promise. LAMP assays, using carefully designed primers, can detect B. pseudomallei DNA rapidly, even in low-resource settings. (Farook et al., 2025) Closed-tube LAMP platforms minimize contamination risks, enhancing reliability. If implemented widely, such molecular tools could democratize diagnosis—bringing accurate, same-day detection to rural health centres.

Genotyping and molecular epidemiology

Genotyping studies from India and South Asia show remarkable genetic diversity in B. pseudomallei. An Indian study found nearly 94% of isolates with novel allelic profiles, with ST-1368 as the predominant founder genotype. (Tellapragada et al., 2016) In Bangladesh, ST-1005 appeared in both soil and clinical samples from Gazipur. Regionally persistent ST-56 has been reported across Myanmar, Thailand, Cambodia and Vietnam, while ST-54, known from Malaysia and nearby areas, also recurs in South Asia. (Jilani et al., 2023) These findings underscore wide phylogeographic connectivity and highlight the need for large-scale studies to clarify environmental reservoirs and the true burden of infection. Comparative analyses show that Indian and South Asian strains are genetically distinct from Australasian isolates but cluster closely with Southeast Asian lineages, indicating shared ancestry and local adaptation. The advent of whole-genome sequencing (WGS) now allows detailed phylogeographic mapping—tracing transmission pathways, outbreak origins, and even emerging virulence or resistance trends.

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