Prevalence vs Incidence

In calculating the risk of diseases afflicting a certain population, authorities use the measures of prevalence and incidence. They are used to determine the rate at which the disease is spreading and the number of people who are at risk.

Both prevalence and incidence are measures of distribution of a disease in a population. While prevalence refers to the total number of cases of the disease in a period of time, incidence refers only to the new cases.
Prevalence in medical parlance refers to the number of cases of a disease in a population during a specific period of time. It is used in reference to how widespread a disease has become and the ratio between those who are already infected and those who are at risk. It is used to determine the total number of cases of a disease in a given population and the impact that it has on society. It includes the length of time that the disease has been encountered and takes into consideration old and new cases.

Incidence, on the other hand, refers to the rate of the manifestation of a certain disease. It is used to measure the rate of occurrence of a disease at a given period usually dealing with the number of new cases that are diagnosed within a population during a specific period.

It provides information on the risk of being afflicted with the disease and is very important in the study of the causes of the disease. In a way, it can be described as a pure measure of risk and provides awareness on how at risk a certain population is in contracting the disease.

For example, in an outbreak of malaria in a certain locality that was widespread in 2008 which caused several cases of death and after a year was restrained, we can say that the malaria outbreak had a high prevalence as well as high incidence during the year 2008.

In the year 2009, however, the incidence will be low but the prevalence remains high because malaria takes time to cure, and a part of the population are still affected and undergoing treatment. A high incidence of a disease will result in a high prevalence, but it does not necessarily follow that high prevalence would also result in a high incidence.

Summary:

1.Prevalence is a measure of the number of cases of a disease in a certain population for a specific period of time while incidence is a measure of the number of new cases of the disease.
2.Prevalence is used to refer to how widespread a disease has become while incidence is used to refer to the rate at which the disease is manifested in a certain population.
3.Prevalence takes into consideration both the number of old and new cases of a disease as well as their duration while incidence only takes into consideration the number of new cases.
4.Compared to prevalence, incidence is more reliable in determining the risk of a certain disease to a population.

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