# Prevalence vs. Incidence

**Difference between Prevalence and Incidence**

Prevalence and incidence are two words which have lot of significance to the medical professionals, scientists and doctors. These are used to indicate the extent to which a disease is spread and to find out the chances of its reoccurrence.

Let s take an example to understand these terms. For example you are working on the treatment of breast cancer in a city. Now, you need to know the actual number of cases of breast cancer in the city and then divide it by the total population of the city. This will give the ratio of prevalence of the disease in the city. To find out the incidence of the disease you need to find out the number of cases which have developed in 1 year. For this you divide the total number of the cases developed in 1 year with the total population. Incidence ratio will always be less than prevalence ratio because in case of incidence we consider the cases which developed in just 1 year.

Incidence ratio is more important factor when we calculate the high risk rate and when we tend to find the risk of a particular population to contract a particular disease. This is helpful in studying etiology.

To understand the difference in a better manner let s summarize the differences between them:

- While calculating prevalence we consider the total number of cases till date while in case of incidence we consider the cases developed in just one year.
- Incidence ratio in most of the cases will be less than prevalence ratio because in case of incidence we consider the cases which developed in just 1 year.