Melioidosis (Burkholderia pseudomallei infection)

Burkholderia pseudomallei lives in wet soil and in water, especially during the rainy season. It is not a germ people usually pass between themselves; the US Centers for Disease Control and Prevention describes person-to-person transmission as very rare. People become infected by breathing in contaminated dust or water droplets, swallowing contaminated food or water, or by contact between contaminated soil and broken skin.

The infection is most associated with Southeast Asia and northern Australia, and the CDC also lists Puerto Rico, the US Virgin Islands and part of the Mississippi Gulf Coast. Cases in the UK are therefore usually linked to travel, with the diagnosis sometimes made weeks or longer after returning home.

Fit people can be infected, but the illness is far more likely to be severe in those with an underlying condition. The CDC lists diabetes, heavy alcohol use, liver disease, kidney disease, thalassaemia, chronic lung disease and weakened immunity. Occupational contact with soil, such as farming, and travel to endemic areas also raise the risk.

This pattern is why the infection is sometimes called a disease of the vulnerable: the bacterium is widespread in the environment, while the host determines how ill the person becomes.

Presentation ranges from a single skin ulcer or abscess to overwhelming bloodstream infection. Symptoms usually emerge within one to three weeks, although the CDC notes that the delay can extend to months or years.

• Localised form: ulcers, nodules or skin abscesses with fever and muscle aches.

• Lung form, the most common: cough, high fever and chest pain, ranging from a mild bronchitis to severe pneumonia, sometimes with chest X-ray changes resembling tuberculosis.

• Disseminated form: abscesses in organs such as the liver, spleen, prostate, joints, bones or brain, and sepsis.

• General signs: fever, headache, breathing difficulty, muscle pain and confusion.

• Chronic form: the CDC reports that about 10 per cent of patients have symptoms lasting at least two months.

Diagnosis is difficult because the picture overlaps with tuberculosis, pneumonia and other tropical infections. Laboratories confirm melioidosis by culturing the bacterium from blood, urine, sputum, cerebrospinal fluid, pus or other samples, or by detecting an antibody response. Telling the clinician and the laboratory about recent travel is essential, because the organism can pose a hazard to laboratory staff and needs careful handling.

The CDC describes an intensive phase of intravenous antibiotics, ceftazidime or meropenem, for between two and eight weeks or longer, followed by an eradication phase of oral antibiotics, usually trimethoprim-sulfamethoxazole or alternatives, for three to six months or more. The long second phase exists because the bacteria can persist, and inadequate treatment risks relapse within one to two years.

Treatment in the UK is under specialist infectious diseases or tropical medicine teams, with microbiology advice. Completing the full course matters even after symptoms have gone.

There is no vaccine. The CDC recommends protective boots and gloves when working with soil, avoiding contact with muddy or contaminated water, covering open wounds, and observing hygiene in healthcare settings. People with diabetes or other risk factors may wish to avoid soil and floodwater contact in endemic areas during the rainy season, and to take medical advice before travel.

Persistent fever, a non-healing ulcer or abscess, cough or chest pain after travel to a tropical area should be reported to a GP or NHS 111 with details of where you travelled and what you did. Sudden breathlessness, confusion or signs of sepsis such as very fast breathing, cold mottled skin or a non-blanching rash require 999.