Anthrax is a life-threatening bacterial infection that is rare in humans but common in grazing animals. Although it is rarely transmitted from one live animal to another, once the victum dies the remaining bacteria can survive as spores indefinitely and exposure to the spores through inhaling or ingesting them, or through a break in the skin, can allow the spores to once again express themselves as bacteria within the host. The bacteria multiplies rapidly and releases toxins as it does so, usually resulting in the death of the patient within a week.
Preventative measures and vaccination have made anthrax rare in modern times. Animals who are suspected of having died of the disease are destroyed and, as a precaution, other animals in the same area are destroyed as well. The spores can travel long distances in water, or even on the wind, so transmission can be rapid.
Anthrax patients requires special handling. They must be immediately quarantined in order to prevent secondary infection from bodily fluids which contain the spores.
In Cursed, Gabe Reillich became exposed to anthrax spores when he tripped and fell on some old hair-felt insulation in an attic. It is not unheard of for spores to last for decades before infecting a new host.