How deadly is anthrax?

Very.: Especially if you inhale the spores. The skin lesions (called "malignant pustules") are not quite as dangerous, but still nothing you want to ever be anywhere near.

Very: Skin, gastrointestinal and pulmonary anthrax are increasingly deadly in the order listed. Pulmonary anthrax, once it becomes apparent, is lethal in almost all cases.

Variable: Mortality rate for untreated cutaneous anthrax is 10 -20 % but less than 1% with correct antibiotic tx. The mortality rate for inhalation anthrax is around 75% (50 - 90 %) even with antibiotic therapy. Mortality rate for gastrointestinal anthrax is about 50 % (25 -60%). Effect of early antibiotic tx is uncertain for GI anthrax. Meningitis due to anthrax is just about 100% fatal.