The employee had been previously immunized for anthrax but has begun antibiotic treatment as a precaution, according to a statement from the base.
Anthrax spores were also detected in a hallway and an administrative room at the U.S. Army Medical Research Institute of Infectious Disease, but appeared to be contained to the area.
The testing was conducted after a scientist noticed a deposit on a flask in a laboratory where anthrax research is performed.
The U.S. Army Medical Research Institute of Infectious Diseases is the Army's germ warfare defense laboratory. Scientists there study the world's deadliest microbes and develop vaccines and antidotes for soldiers who could encounter such pathogens naturally or as targets of biological weapons.