Glanders is primarily a disease of equine species that may occasionally be transmitted to humans. Glanders is rare in most of the world, but is believed still to be endemic in parts of Africa, the Middle East, South and South East Asia, and Turkey.
Melioidosis is caused by an environmental saprophyte found in mud and water in tropical and sub-tropical regions, particularly South and South East Asia and northern Australia.
For both organisms (Burkholderia mallei and B. pseudomallei), it is likely that the natural mode of transmission is mainly by inoculation into small abrasions or by inhalation e.g. during heavy rains. Infection by inhalation is also the most likely route by which infection would occur following deliberate release. Person-to-person spread is extremely rare.