A letter published in the Journal of Environmental and Occupational Medicine, April 2004 described two lab workers using standard procedures to grow and handle anthrax at USAMRIID. Despite this, medium leaked from a flask and spores were recovered from the nares of one of the workers. The potential for inhalation anthrax was considered serious, and the worker received an extra vaccine booster dose and both took cipro for a month.
There was also a case of cutaneous anthrax reported in a lab worker in Texas in 2002 (MMWR 2002;51:482). It appears Ivins' accident was by no means a unique event.