(a) : Small pox is an acute highly communicable disease. It is caused by virus named Variola virus. Now it is eradicated from world including India. It is highly infectious disease starting with high fever, chill, backache and headache, followed by appearance of rash on the third day of illness. The rash appears first on the face, then on the rest of the body. The rash starts as small reddish spots which change into papules. These in turn change into small vesicles containing clear fluid. Vesicles change into postules. Finally, a scab is formed and it falls off by the third week. These scabs leave deep pits or scars known as pock marks. The virus is present in the oral and nasal discharges of the patients and is ejected during the acts of coughing, sneezing, etc., and infects the healthy people.