Melioidosis is an infection caused by the Gram-negative bacillus Burkholderia pseudomallei, which is naturally found in water and soil in areas endemic for melioidosis. Infection can be severe and sometimes fatal. The federal select agent program designates B. pseudomallei as a Tier 1 overlap select agent, which can affect both humans and animals. Identification of B. pseudomallei and all occupational exposures must be reported to the Federal Select Agent Program immediately (i.e., within 24 hours), whereas states are not required to notify CDC's Bacterial Special Pathogens Branch (BSPB) of human infections.
The passive surveillance system includes reports of suspected (human and animal) melioidosis cases and reports of incidents of possible occupational exposures. Reporting of suspected cases to BSPB is voluntary. BSPB receives reports of occupational exposure in the context of a request for technical consultation (so that the system does not include the full complement of the mandatory and confidential reporting to the Federal Select Agent Program). Reporting sources include state health departments, medical facilities, microbiologic laboratories, or research facilities. Melioidosis cases are classified using the standard case definition adopted by the Council of State and Territorial Epidemiologists in 2011. In follow up to reports of occupational exposures, CDC often provides technical assistance to state health departments to identify all persons with possible exposures, define level of risk, and provide recommendations for postexposure prophylaxis and health monitoring of exposed persons.
During 2008-2013, BSPB provided technical assistance to 20 U.S. states and Puerto Rico involving 37 confirmed cases of melioidosis (34 human cases and three animal cases). Among those with documented travel history, the majority of reported cases (64%) occurred among persons with a documented travel history to areas endemic for melioidosis. Two persons did not report any travel outside of the United States. Separately, six incidents of possible occupational exposure involving research activities also were reported to BSPB, for which two incidents involved occupational exposures and no human infections occurred. Technical assistance was not required for these incidents because of risk-level (low or none) and appropriate onsite occupational safety response. Of the 261 persons at risk for occupational exposure to B. pseudomallei while performing laboratory diagnostics, 43 (16%) persons had high-risk exposures, 130 (50%) persons had low-risk exposures, and 88 (34%) persons were classified as having undetermined or unknown risk.
A small number of U.S. cases of melioidosis have been reported among persons with no travel history outside of the United States, whereas the majority of cases have occurred in persons with a travel history to areas endemic for melioidosis. If the number of travelers continues to increase in countries where the disease is endemic, the likelihood of identifying imported melioidosis cases in the United States might also increase.
Reporting of melioidosis cases can improve the ability to monitor the incidence and prevalence of the disease in the United States. To improve prevention and control of melioidosis, CDC recommends that (1) physicians consider melioidosis in the differential diagnosis of patients with acute febrile illnesses, risk factors for melioidosis, and compatible travel or exposure history; (2) personnel at risk for occupational exposure (e.g., laboratory workers or researchers) follow proper safety practices, which includes using appropriate personal protective equipment when working with unknown pathogens; and (3) all possible occupational exposures to B. pseudomallei be reported voluntarily to BSPB.