The source of this patient's infection remains unknown. However, genomic analysis showed that the patient isolate groups with existing isolates collected from other patients in the southwestern United States. Isolates TX2004 and TX2018b were collected ≈15 years apart from patients living in the same Texas county at time of illness onset and group together, a finding that suggests B. pseudomallei might be present in the environment in this area. Furthermore, these 2 isolates might represent a new clade endemic to the continental United States. Further investigation is warranted because this region is predicted to have suitable habitats for B. pseudomallei.
These findings call into question possible reactivation of melioidosis decades after travel to melioidosis-endemic regions. Instead of a 62-year incubation period, the patient infected with TX2004 might have had an unknown local environmental exposure that preceded symptom onset. A 1991 case report of an 18-year latency for a Vietnam War veteran indicated that this patient was also living in the southwestern United States (New Mexico) at time of symptom onset and had not traveled outside the continental United States since 1971. On the other hand, although geographic and genotypic links between the 2 Texas cases suggest a local source, B. pseudomallei exposure for the patient infected with TX2018b could have occurred 30 years earlier, while visiting Mexico, and the patient infected with TX2004 might have had unreported regional travel before illness onset. Only when B. pseudomallei is isolated from the environment can it be definitively stated that B. pseudomallei is endemic to the continental United States.
B. pseudomallei infection should be included in a differential diagnosis for a patient with compatible disease, even without reported travel history. Increased awareness among healthcare workers and diagnostic laboratory personnel for melioidosis as a disease potentially endemic to the southwestern United States is critical to improve case outcomes and prevent laboratory exposures.
In addition, melioidosis is caused by a Tier 1 overlap Select Agent, but reporting of cases to CDC is voluntary.[2,7] Making melioidosis nationally notifiable could improve surveillance and recognition and clarify distribution and potential sources of B. pseudomallei infection in the United States.
We thank the patient and his family for providing photographs of the patient's progressing cutaneous chest wound and the Arizona Department of Health and Maricopa County Department of Health for providing background information on strain AZ1999.
Emerging Infectious Diseases. 2020;26(6):1295-1299. © 2020 Centers for Disease Control and Prevention (CDC)