You can use a laminar flow hood and disinfectant. Plus, it takes 10,000 spores in the lungs to give you pulmonary Anthrax. They can afford to breathe in a few.
Be that as it may, given the disregard for their own lives these animals have displayed, it's also reasonable to assume that the sleeper agent/cell stuffing envelopes is by now infected. That should mean:
1/ He/They'll mail out their rermaining supplies in a rash of letters (which, hopefully, we may just have seen); and,
2/ If he/they are infected, what stunt have he/they got in mind to make a dramatic exit? In other words, the liklihood of being infection increases the chances of another attack.
In the article it states:
One indicator, Spertzel says, is particle size. Inducing pulmonary, or inhaled, anthrax requires 8,000 to 10,000 spores embedded in particles between one to five microns in diameter. That amount would fit on the period at the end of this sentence.
This indicates that just one 5 micron particle may have enough spores to infect you. Two, definitely.