Epidemiology, Clinical Features, and Outcomes of Chronic Melioidosis in the Top End of Australia's Northern Territory, 1989–2023

Background Melioidosis is caused by infection with Burkholderia pseudomallei. Most cases present acutely however a minority have chronic symptoms. We aimed to define the clinical epidemiology of chronic melioidosis. Method Cases of melioidosis with symptoms for ≥2 months in the Australian Northern Territory from 1989 to 2023 were described and compared to cases with symptoms for <2 months. Results Among the 126 (9.4%) chronic melioidosis cases, the most common presentations were pneumonia (38.9%) and skin and soft tissue infections (32.5%). In those with primary pneumonia, neoplasia was a differential diagnosis in 25.5% and tuberculosis in 32.4% of chest radiography reports. Patients with chronic compared to acute melioidosis were significantly more likely to have cutaneous disease (32.5% vs 10.4%, P < .001) and less likely to have pneumonia (38.9% vs 53.6%, P = .002), have positive blood cultures (14.3% vs 59.1%, P < .001), have more than one infective focus (13.5% vs 22.5%, P = .019), or die from their initial melioidosis episode (2.4% vs 11.1%, P = .003). Those with chronic presentations were less likely to be diagnosed in the wet season (55.6% vs 83.9%, P < .001), be First Nations Australians (35.7% vs 54.8%, P < .001), or have clinical risk factors for melioidosis including diabetes mellitus (32.5% vs 48.0%, P < .001), chronic kidney disease (6.4% vs 12.4%, P = .046), and hazardous alcohol use (27.0% vs 40.3%, P = .003). Serology by indirect hemagglutination assay was positive at diagnosis in 87.0% of chronic presentations compared to 48.5% of acute cases. Conclusions Patients with chronic melioidosis have fewer risk factors for melioidosis, lower disease severity, higher serology titers, and lower mortality than patients with acute melioidosis.