They warn that the number of patients with diabetes mellitus is also increasing.

According to a paper published online on Monday in Nature Microbiology, melioidosis is likely to be present in many more countries than previously thought. It is reportedly present in 79 countries, including 34 that have never reported it before.

The paper recommends that health workers and policy makers give melioidosis higher priority. It expects the number of melioidosis cases to rise as diabetes increases across the tropics, especially among the poor. International travel also increases the risk of introducing the pathogen to new areas.

“Although melioidosis has been recognised for more than 100 years, awareness of it is still low, even among medical and laboratory staff in confirmed endemic areas,” said study co-author Mahidol University (MU) assistant professor Dr Direk Limmathurotsakul.

“We predict that the burden of this disease is likely to increase in the future because the incidence of diabetes mellitus is increasing and the movement of people and animals could lead to the establishment of new endemic areas,” he said.

Direk is also Head of Microbiology at Mahidol Oxford Tropical Medicine Research Unit (MORU) in Bangkok.

The study is the first to provide an evidence-based estimate of the global extent of melioidosis, which is caused by Burkholderia pseudomallei, a highly pathogenic bacterium commonly found in soil and water in South and Southeast Asia and northern Australia.

The study funded by the Wellcome Trust (UK) was carried out by researchers at the Oxford University in the UK, the MORU, the University of Washington in Seattle and the MU and allies.

Highest risk

The highest melioidosis-risk areas are in South Asia, East Asia and the Pacific, including all countries in Southeast Asia and tropical Australia, sub-Saharan Africa and South America, with risk zones of varying sizes in Central America, southern Africa and the Middle East.

Contracted through the skin, lungs or by drinking contaminated water, melioidosis can be difficult to diagnose as it mimics other diseases. As a result, a good microbiology laboratory for bacterial culture and identification was needed for an accurate diagnosis, Direk said.

“Melioidosis especially affects the rural poor in the tropics, who often do not have access to microbiology labs, which means that it has been greatly under-estimated as an important public health problem across the world,” he said. “Our study predicts high infection rates in countries like India and Vietnam, where the disease is gradually being recognised more frequently.”

The bacterium is resistant to a wide range of antimicrobials, and inadequate treatment may result in case fatality rates exceeding 70 per cent.

The study estimates that melioidosis killed 89,000 of the 165,000 people who got it in 2015 – nearly as many as the annual global mortality from measles (95,000 deaths per year) and greater than deaths from leptospirosis (50,000 per year) or dengue (12,500 per year).