Clinical features of acute melioidosis

The majority of infections with Burkholderia pseudomallei are asymptomatic. In disease, theincubation period, clinical presentations of melioidosis, and outcomes are thought to be determined by a combination of bacterial load infecting the individual, putative B. pseudomallei strain differences in virulence, mode of infection and, most importantly, host risk factors for disease. Over 85% of cases of melioidosis are acute presentations, with an incubation period of 1 to 21 days (mean, nine days). Mortality varies depending upon disease severity and access to diagnostic and therapeutic facilities, ranging from over 90% in patients presenting with disseminated disease and septic shock in under-resourced rural locations, to potentially zero in patients without any risk factors who present with localised disease (for example, cutaneous melioidosis). Bacteraemia occursin 40 to 60% of cases, and around half of patients present with pneumonia. Other presentations include: cutaneous melioidosis; septic arthritis and/or osteomyelitis; genitourinary presentations, most notably prostatic abscesses; suppurative parotitis, seen commonly in children in Thailand; bacteraemia without an evident clinical focus; and melioidosis meningo-encephalitis, as seen morecommonly in Australia than elsewhere. Internal organ abscesses are common, as is secondarybacteraemic spread to other foci irrespective of the primary presentation.