Melioidosis is an infection caused by the gram-negative bacillus Burkholderia pseudomallei. The disease is most commonly seen in tropical climates. The pathogen is generally found in soil, and transmission can occur when heavy rains after a dry spell result in increased presence of the pathogen in soil and surface water, and even aerosolization (in the setting of heavy monsoon rains in certain geographies for example). It is endemic to Southeast Asia and northern Australia with most cases occurring during the rainy season. It may also be found in the South Pacific, Africa, India, the Middle East, and Central and South America. In endemic areas, military personnel, agricultural workers, farmers, gardeners, and tourists are at higher risk for contracting melioidosis. Patients with AIDS in endemic areas are susceptible to infection.

Note: In the United States, consider melioidosis in patients with a compatible illness even if they do not have a travel history to a disease-endemic country. Between March and July 2021, the US Centers for Disease Control and Prevention (CDC) identified a multistate cluster of nontravel-associated B pseudomallei infections in 4 patients from Georgia, Kansas, Texas, and Minnesota. Infection was likely a consequence of long dry spells followed by heavy rains aerosolizing the pathogen. On July 27, 2022, the CDC issued a health advisory for melioidosis in the Gulf Coast region of the United States. Burkholderia pseudomallei was identified for the first time in the environment in the continental United States through environmental sampling of soil and water in the Gulf Coast region of southern Mississippi during an investigation of two human melioidosis cases.

Melioidosis is acquired through skin abrasions, inhalation, and other types of contact with contaminated water and soil. There are 4 clinically distinct types of melioidosis: localized, pulmonary, bacteremia (septicemic), and disseminated. Melioidosis is usually nonfatal, except in the septicemic form.

Localized
Acute localized melioidosis usually presents with a skin nodule or pustule. The skin lesions typically occur 1-5 days following an initial bacterial inoculation through a break in the skin from contaminated water or soil. Lymphadenitis and regional lymphadenopathy are common. Associated systemic symptoms may include fever, chills, and myalgias. It may progress to septicemia, especially in immunocompromised patients or the chronically ill.

Pulmonary
Pulmonary melioidosis has a clinical presentation that can vary from a mild bronchitis to a severe pneumonia. Symptoms occur 10-14 days after inhalation of aerosolized bacteria and include sudden onset of high fever, chills, productive or nonproductive cough, chest pain, headache, anorexia, and myalgia. This is the only form of melioidosis that presents with a cough. Skin abscesses may be seen, even months after infection.

Bacteremia (Septicemic)
Bacteremia due to B pseudomallei (septicemic melioidosis) usually results in septic shock and is most likely to occur in the immunocompromised and those with diabetes and renal insufficiency. Symptoms include headache, fever, chills, diarrhea, disseminated abscesses, myalgia, skin pustules, disorientation, and respiratory distress. Mortality rates are at least 90%, and death may occur within 48 hours, even with therapy. Patients with diabetes, cirrhosis, lung disease, renal disease, or cystic fibrosis, the immunocompromised, and those who consume kava root are predisposed to septicemic infection.

Disseminated
Disseminated or chronic suppurative melioidosis usually has a delayed onset and presents with abscesses in organs such as the skin, brain, liver, lungs, and spleen. It may also produce abscesses in the lymphatics, bones, and joints.

The incubation period of melioidosis can vary anywhere between 2 days and years. Person-to-person transmission is possible, including sexual transmission. Currently there is no vaccine for melioidosis.

Note: Wear protective clothing and footwear in endemic areas.