1.   The anthrax that was disseminated last fall was in the form of spores, which is the infectious form, Koehler said.

2.   The changes in the virus transformed it from a benign organism intended to provoke immunity to an infectious form that could cause disease.

3.   To become so nastily infected, a person must swallow oocysts, the tough capsules that shelter the infectious form of the parasite.

4.   A scientist leading research into the bird flu outbreak warned Wednesday that the virus could mutate into a form infectious for humans.