Plague is referred to be an ancient scourge of mankind. The disease was familiar to the ancient civilization of Asia. The home of plague is recognized to be Central Asia from where it evolved.
The name ‘black death evolved from the extensive and cutaneous hemorrhage and gangrene that was seen in the fatal cases of plague. In humans, plague is seen to occur in three major forms namely, bubonic, pneumonic and septicemic. In bubonic plague, after an incubation period of two to five days, the lymph node draining the site of entry of the bacillus becomes infected.
Pneumonic plague may be seen sometimes during epidermis of bubonic plague. Septicemic plague is considered to be the terminal event in bubonic or pneumonic plague but at many times also seen to occur primarily. Meningitis involvement is also seen to occur very rarely. Human carriers are yet not recorded but asymptomatic oropharyngeal infection has been observed in contacts.