What is Epidemic Disease ?

The term epidemic originally denotes a sudden excessive prevalence of the disease in a population. Epidemic means upon the people. Historically, the epidemic was applied to infectious disease, but in more recent times, it also includes major non-infectious diseases, such as AIDs, Covid-19, and cancer, too.

The main epidemics in India are malaria, small-pox, cholera, typhoid, dengue, swine flu, cancer, AIDs, etc. AIDs according to a UN report caused 1,30,000 deaths in 2013. Recently, Covid-19 has been declared as the biggest epidemic in the world. Ebola fever in West Africa (Guinea, Sierra-Leone, Liberia, etc.) has emerged as a serious epidemics during the last decade.


Epidemic diseases are transmitted in many ways. Some of the ways of their transmission are as under:

  • By direct contact, for example, droplets sprayed about when a patient coughs or sneezes.
  • By contaminated food and water.
  • By arthropods — filth associated files — of various types that may serve as mechanical carriers of disease germs as in dysentery and cholera. Blood-sucking arthropods like mosquitoes are more effective transmitters.

Factors Affecting the Incidence

Apart from weather and climate, there are many factors which influence the spread and intensity of epidemics. Some of the factors are:

  • ethnicity,
  • age and sex composition,
  • literacy and education,
  • occupation and lifestyle,
  • standard of living,
  • size of family and degree of crowding,
  • residential locality,
  • food habits,
  • smoking and consumption of liquor, and
  • association with animals and birds.

Incidence Curve

Incidence curve of different epidemic diseases is similar in that the rise in a number of cases in an epidemic is usually more rapid than its fall.