Epidemics generally follow a pattern depending on the geographical and environmental conditions, the distribution and characteristics of the host population, and their cultural behavior. If there is no intervention or change in these conditions, those epidemics tend to repeat themselves. Therefore, knowledge about various types of epidemics and the conditions under which they occur can be of help in managing them.

The various types of epidemics that normally occur are described given below:

i) Common Source Epidemics

These epidemics originate from a single source of infection of the disease-producing agent. There are two types of common source epidemics:

a) Point source or single exposure epidemics

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In this type of epidemic the disease agent responsible for spread of disease is exposed to susceptible population at one point of time and only once. A very good example of this type of epidemic is occurrence of food poisoning due to consumption of contaminated food in a feast. In this type of epidemic, there is a sudden rise of cases, which decline equally fast.

b) Continuous or multiple exposure epidemics

In this type of epidemic, the source of infection is continuous and such epidemics will not cease to exist unless the source is removed. A well with contaminated water becomes a regular source of infection to the people using it and the epidemic may continue until the water is treated and made safe. Similarly, a cook who is a disease carrier may keep on infecting the diners in the restaurant till he is treated and made non-infectious.

ii) Propagated Epidemics

A propagated epidemic is generally of infectious origin and results from person to person transmission of disease agents. The epidemic shows a gradual rise and tapers slowly over a period of time. Transmission continues until there are no susceptible individuals. Such epidemics are more likely where large number of susceptible individuals gather as in fairs and festivals.

iii) Seasonal Epidemics

Certain diseases such as influenza and pneumonia are more common during winter season where as diarrhea diseases are more during summer and rainy seasons. The epidemics, which occur in particular season, are known as seasonal epidemics.

iv) Cyclical Epidemics

Some epidemics tend to occur in cycles, which may repeat over a period of time, which may be days, weeks, months or years. An example of this type of epidemic is measles V which tends to occur in a cycle of 2-3years.

v) Epidemic of Non-communicable Diseases

With the advances in science and technology, the changing life styles have led to living pattern, which is sedentary and affluent with little physical activity. This has resulted in a marked rise in diseases like hypertension, heart diseases, diabetes and mental diseases. The non-communicable diseases are acquired epidemic proportions in recent times.