The relevant authorities responsible for maintaining public health such as local authorities, health trusts, government institutions, voluntary organizations etc are required to measure, monitor and control the incidence of different diseases and conditions which occur in a community. In epidemiology, incidence is a measure of a person’s likelihood or risk of developing some new disease within a specified time period and is best expressed as a rate or a probability. Incidence is also a mathematical quantity that describes the occurrence of a disease Y in a population. It is the proportion of persons in the population, who newly develop the disease Y within a given time period (t): The measure of incidence is stated below:

Incidence in population P  =  

# who develop the disease Y in population p in a time t

# in population p

The practice of disease monitoring is a complex subject and the method implemented in order to carry out this practice varies slightly according the nature of the disease and