Anthrax can infect humans in three ways. The most common is infection through the skin, which causes an ugly, dark sore. Humans and animals can ingest anthrax from carcasses of dead animals that have been contaminated with anthrax. Ingestion of anthrax can cause serious, sometimes fatal disease. The most deadly form is inhalation anthrax. If the spores of anthrax are inhaled, they migrate to lymph glands in the chest where they proliferate, spread, and produce toxins that often cause death.