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Clinical Characteristics

Prior to the 1960s war in Southeast Asia, melioidosis was believed to be a rare and almost uniformly fatal disease. Reports up to the early 1960s showed few survivors and, in many, the cause of death was not recognized until autopsy. In 1961 and 1963, Nigg demonstrated a high incidence of asymptomatic or subclinical infections in Thailand. He found that over 8% of apparently healthy Thai adults had a positive complement fixation test and 29% had a positive hemagglutination reaction. Ashdown and Guard found an overall melioidosis antibody rate of 5.7% among 9000 individuals in northern Queensland, Australia, with rates up to 15% in alcoholics, diabetics, and those with liver disease. From these and other surveys, it became clear that many people in endemic areas had been exposed to the organism and survived. Either they had a subclinical infection or had been totally asymptomatic, in contrast to the 80-95% mortality figures quoted in the earlier literature. In fact, the mortality rate in all forms of melioidosis except the septicemic form is low. Even with high doses of antibiotics and vigorous supportive therapy, the mortality remains high in septicemic melioidosis (at least 37% in most series of patients). Few survivors have had long term follow-up, but the incidence of late relapse appears to be high.

The majority of those exposed are probably unrecognized because they have no illness or complaints. Moreover, because the disease can easily be confused with tuberculosis, fungal and other infections, it is probable that numerous cases are misdiagnosed clinically, radiologically, and in the laboratory. It is not always easy to differentiate the causative bacterium from other more common gram-negative bacilli. As with other infections, a high level of suspicion is required when there is a history of travel or residence in an endemic area such as Southeast Asia, and the patient has a chest roentgenogram showing either an upper lobe density, often with cavitation, or diffuse small, irregular pulmonary nodules.

The American involvement in the Vietnam War and the concomitant infection of several hundred U.S. soldiers with melioidosis provided abundant case material to study this disease in depth. In one series, 30 patients with proven melioidosis were studied in U.S. Army hospitals from 1965 to 1970. These patients had their disease documented by either serological studies or cultures, and roentgenograms obtained on admission and/or subsequently during their hospitalization were reviewed and correlated with the clinical presentation. From this and other series, it is apparent that there are four different ways in which a patient with melioidosis may present.

1. Acute: Patients present with severe prostration, chills and fever of 38°-40°C (102°-104°F). There is a prodromal period of 1-7 days (Figs. 23.6-23.11).

2. Subacute: Patients present with chest pain, occasional blood-streaked sputum, a low grade fever, and weight loss. There is a prodromal period of weeks or months (Figs. 23.12-23.18).

3. Subclinical: Patients have few or no symptoms; the disease is suspected because of an abnormal chest roentgenogram and/or serological studies. The prodromal period is unknown (Figs. 23.19-23.22).

4. Chronic (usually extrapulmonary): In these patients, skin lesions or, occasionally, osteomyelitis are the usual primary sites of infection. The prodromal period is variable (Figs. 23.23-23.25).

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Copyright: Palmer and Reeder