In Epidemology, when an infection is contantly existing in a particular area of a region or population, it is said to be endemic.
Example: Chicken pox in United Kingdom , Malaria in Africa.
Types of Endemic :
In holoendemic almost every individual in a population is infected essentially. Although the infection is present everywhere in that region,the adult people do show any traces or symptoms of the disease due to adaptive immunity.the young are likely to show pathogenic responses while the older just carry the disease asymptomatically.
Malaria is a type of holoendemic disease.
Hyperendemic refers to continuing firmly and high levels of disease occurrence.These type of endemic disease are constantly present at high rate and are found among all age groups equally.
This denotes a population or area of a region in which the rate of new cases of disease is sufficiently low that the population has limited or no immunity to it.
In Epidemology, when a disease is spread rapidy and unexpectedly to large number of people over a wide geoographic area.
It refers to an increase, often sudden in number of cases of disease beyond what is normally expected in the population of the area.
The disease will spread normally in two weeks or less in case of epidemic.
Sometimes epidemics may be the consequence of tropical storms, floods, droughts and earthquakes.
Examples: The outbreaks of zika virus ,chikungunya and dengue fever in the past are examples of epedemics in india
An epidemic of disease is when a significant and ongoing person to person spread is across multiple countries , multiple continents or worldwide then it is called pandemic.
But if a widespread endemic disease with stable number of infected people is not a pandemic.
A pandemic infects more people and causes more deaths than epidemic
WHO defines pandemic as the new pathogen that spreads easily from person to person across the globe
Examples: smallpox , cholera and COVID-19.