Melioidosis and Activation from Latency: The "Time Bomb" Has Not Occurred.

Burkholderia pseudomallei, the causative agent of melioidosis has long been considered able to exist in a latent form. Seropositivity among U.S. soldiers returning from the Vietnam conflict led to melioidosis being dubbed "the Vietnamese time bomb." Cases assigned to "(re)activation from latency" over 30 years of the Darwin Prospective Melioidosis Study (DPMS) were reviewed and reassessed and additional cases from DPMS years 31-34 were added. Historical reports of melioidosis attributed to activation from latency were reviewed. Some earlier DPMS cases and most historical cases described as activation from latency more accurately reflect undiagnosed chronic melioidosis, often with relapsing-remitting courses, rather than truly latent, asymptomatic infection. Such protracted disease should now be diagnosable much earlier, provided melioidosis is considered and laboratory facilities are available. The longest plausible duration of asymptomatic latency remains 29 years. In conclusion, activation from latency is a rare event in melioidosis, accounting in our analysis for under 3% of DPMS cases, consistent with why the Vietnamese time bomb never eventuated.