Environmental mapping reveals melioidosis in Odisha peak during monsoon

Environmental conditions are primarily responsible for the survival of the bacteria
| Photo Credit: Dr. Todd Parker

Globally, research on climate/environmentally driven infectious diseases has been largely biased towards vector-borne diseases like malaria, dengue, etc. Melioidosis is a bacterial infectious disease caused by Burkholderia pseudomallei, and is primarily acquired by inoculation, inhalation and/or ingestion of soil- and water-dwelling environmental saprophytes. The disease is strongly influenced by environmental factors such as rainfall, temperature, and humidity. In 2016, The Lancet based on a prediction modelling study reported that about 1,65,000 people contract melioidosis annually worldwide, of which Southasia, including India, contributes to 44% of the global burden of melioidosis. The report attracted enormous scrutiny and attention by the medical fraternity, and microbiologists and clinicians in a few selected centres across India took cognisance of the situation to further unravel the mysterious disease.

There are many reasons why the melioidosis-causing bacteria, described over a hundred years ago, has continued to baffle the medical fraternity. First, the bacteria has a unique ability to cause a plethora of clinical manifestations ranging from a trivial skin infection to unresolving pneumonia and fulminant sepsis. With fatality as high as 50% in septicaemic cases, melioidosis is a medical conundrum. Second, the B. pseudomallei bacteria requires prolonged incubation conditions, and can escape detection in inexperienced microbiology laboratories, as chances of misidentification with common bacteria like Pseudomonas aeruginosa are quite common. Third, the treatment of melioidosis is quite different from other infectious diseases as it requires an initial intravenous therapy followed by a prolonged eradication phase of 12-20 weeks. This puts a significant emphasis on correct diagnosis, as inadequate treatment runs a risk of recurrence.  

In India, melioidosis research has mainly focused on understanding the disease from the host perspective like presence of comorbidities like diabetes, chronic renal diseases etc and occupational factors like farming and behavioural  factors like alcoholism, which increases the likelihood of diseases. In Odisha, melioidosis cases are being reported at AIIMS Bhubaneswar, with cases increasing over the years.

Odisha with vast agricultural areas and extreme weather events present ample opportunities for human exposure to the bacteria. Environmental conditions are primarily responsible for the survival of the melioidosis-causing bacteria, thus making a strong case for investigation. With this in mind, microbiologists at AIIMS Bhubaneswar and climate scientists at IIT Bhubaneswar have collaborated to identify and track the conditions that may facilitate the occurrence of melioidosis in Odisha. To investigate this, the team tracked each reported disease case, correlating it with the patient’s home location and possible incubation periods to identify the most common environmental conditions that may have facilitated disease transmission. The study focused on 144 disease cases over a nine-year period from 2015 to 2023. The team analysed meteorological parameters, including rainfall, temperature, humidity, and solar radiation, across more than 3,024 days during this period to identify the most favourable conditions for bacterial survival and, consequently, transmission. Using this information, the team created a map identifying potential regions for disease occurrence, using 10 km grid sizes to cover the entire State of Odisha. 

The analysis, which was recently published in the journal Current Research in Microbial Sciences, revealed that the disease exhibited a clear seasonality, with infections peaking during and after the monsoon season. Disease occurrence also exhibited relationships with temperature, rainfall, cloud cover and solar radiation. The mapping indicated that districts such as Cuttack, Balasore, Khordha, and Jajpur have a high potential for disease occurrence. Interestingly, these areas also coincide with some of the most densely populated regions in the State. Other elements, such as land use changes, soil composition, are likely to influence disease dynamics. Due to data limitations, the team was unable to include these factors in the study. Rapid urbanisation, poor sanitation, may further heighten risk by increasing human exposure to contaminated environments. Additionally, as climate change alters rainfall patterns and intensifies extreme weather events, these diseases could become more widespread and/or shift to new regions. Therefore, public health systems must adapt by incorporating climate analytics into their disease surveillance and prediction efforts.

This study also highlights the potential of climate-driven disease modeling beyond melioidosis, especially for diseases influenced by environmental factors. Incorporating weather and climate data into public health planning could improve outbreak predictions, enhance preparedness, and reduce health risks. Odisha’s experience could provide a valuable model for other regions, highlighting the importance of combining climate science with medical research to address emerging health risks.

(B. Behera is Professor, Department of Microbiology, AIIMS Bhubaneswar; T.S. Sarin is PhD scholar at the School of Earth Ocean and Climate Sciences, IIT Bhubaneswar; and V. Vinoj is Associate Professor, School of Earth Ocean and Climate Sciences, IIT Bhubaneswar)