Is anthrax severe?

Can be. Pulmonary anthrax can be deadly within days. Other forma, not so problamatic but worthy of agressive treatment. See www.Bt.Cdc.Gov/agent/anthrax.
Possible. Anthrax can be severe. If you think you have been exposed see a physician.
Yes. Fatality is greatest for pulmonary anthrax & least for cutaneous with GI lying in the middle.Mortality rate for untreated cutaneous anthrax is 10 -20 percent 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%). Anthrax memingitis - 100%.