Anthrax bacteria and biohazard symbol. Biohazard warning symbol (orange) on a coloured transmission electron micrograph (TEM) of a section through Bacillus anthracis bacteria (blue). These are the cause of anthrax, a disease used in biological warfare and terrorism. The disease is transmitted from infected animal carcasses or by inhalation of the spores (not seen) that the bacteria produce. Spore inhalation can lead to pulmonary anthrax (the infection of the lungs). This rare form of the disease is generally fatal if not treated with antibiotic drugs before the onset of the flu-like symptoms. The skin form of anthrax is more common and easier to treat. Magnification unknown.