Epidemiology

The estimated annual global burden of melioidosis is approximately 165,000 cases, including 89,000 deaths. It occurs in people of all ages, but the peak incidence is in adults aged 40-60 years.[22] It accounts for 4.6 million disability-adjusted life years globally (or 84 per 100,000 population).[23]

Melioidosis has traditionally been thought of as a disease of Southeast Asia and northern Australia, but over the past 20 years it has been increasingly recognised throughout the tropics, including the Indian subcontinent, sub-Saharan Africa, and Central and South America and the Caribbean.[24] The greatest number of cases are reported from Thailand (especially the north east), Malaysia, Singapore, and northern Australia. However, modelling suggests that it is greatly under-diagnosed in most of the 45 countries in which it is known to be endemic, and may be present in a further 34 countries where it has not yet been reported.[25]

A small number of imported cases are also regularly seen in non-endemic areas (e.g., France, the Netherlands, the US, Saudi Arabia, China).[26][27][28][29][30]​​ A small number of cases were reported in Georgia in the US in August 2021.[31]​ An outbreak of four cases in Texas in 2021 was associated with an aromatherapy spray imported from India.[32]​ Two cases have also been reported in the gulf coast region of southern Mississippi, with Burholderia pseudomallei isolated in local soil and water, the first time the bacterium has been identified in the environment in the continental US.[33]

Within endemic areas, the disease predominantly affects those with regular soil and water contact (e.g., rice farmers in Southeast Asia and Aboriginal people in Australia), although even those with no obvious direct contact with the environment may become infected. One of the main reasons the disease is under-recognised is because the rural poor in the tropics rarely have access to the microbiology laboratories that are needed to confirm the diagnosis. In most places the disease is highly seasonal, with rainy season peaks corresponding to the time when exposure is most likely. Infection occurs in all age groups, with a small peak in children, many of whom have relatively mild, localised infections,[10] and a larger peak in adults aged from 40 to 70 years.[7][34] In the latter group, some 55% to 80% of patients have an underlying disease that predisposes them to melioidosis, particularly diabetes mellitus; chronic renal, liver, or lung disease; excessive alcohol intake or binge drinking; corticosteroid use; or thalassaemia. HIV infection does not seem to lead to an increased risk of melioidosis, although co-infections have occasionally been reported. Diabetes appears to be particularly strongly associated with a risk of infection, for reasons that are not yet fully understood, but melioidosis may thus be expected to become more common as the prevalence of diabetes increases in the tropics. Males are usually more frequently affected than females, although the proportions vary from place to place, probably reflecting cultural differences that affect the likelihood of soil and water exposure.

Glanders is a disease that really only existed as a significant human public health issue for just over 100 years, between its first description in 1812 and the 1940s and 1950s when the last naturally acquired cases were reported in the US and Europe. However, equine glanders still occurs in parts of Africa, Asia, the Middle East, and Central and South America, and laboratory-acquired infection may also occur, so the potential for human glanders to occur remains.[35]

[Figure caption and citation for the preceding image starts]: Endemicity of melioidosis infectionCDC [Citation ends].com.bmj.content.model.Caption@1b9aaef0

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