The epidemic trio: pandemic, epidemic, endemic
An epidemic is an infectious disease that can spread rapidly and affects many people. In terms of the temporal and spatial extent of epidemics, physicians distinguish between three forms: Pandemic, Epidemic and Endemic.
Pandemic: Definition
A pandemic is a worldwide epidemic. In this case, an infectious disease occurs in large numbers over a limited period of time. While an epidemic is limited to individual regions, a pandemic spreads across national borders and continents. The most recent example is the Covid 19 pandemic.
Triggered by the SARS-CoV-2 coronavirus, this disease spread rapidly across the planet. It started in China in December 2019. As early as March 2020, the World Health Organization (WHO) spoke of a pandemic.
In the meantime, a large part of the global population has survived the infection or has been vaccinated against the coronavirus. Nevertheless, according to current expert opinion, the virus and Covid-19 will not disappear completely and people will fall ill again and again. Experts expect Covid-19 to eventually become endemic (see below for definition).
Epidemic: Definition
Epidemics naturally occur much more frequently than pandemics. Physicians distinguish between two forms of epidemics, depending on the dynamics of their spread:
- Tardive epidemic: Here, the number of cases rises slowly and also falls only slowly again. These are pathogens that are transmitted via direct contact (often mucosal contact). One example of this was HIV.
Endemic: Definition
The third form of epidemic is the endemic: Here, the clustered occurrence of an infectious disease is spatially limited, as in an epidemic. However, unlike epidemics and pandemics, an endemic is not limited in time. It occurs permanently in a specific region.
Such endemic areas exist, for example, in the case of yellow fever. They are located in (sub-)tropical Africa and South America.
Overview: Difference between pandemic, epidemic and endemic
The following table shows at a glance the similarities and differences between pandemic, epidemic and endemic:
|
Type of epidemic |
spatial extent |
temporal extent |
|
Epidemic |
spatially limited |
temporally limited |
|
Endemic |
spatially limited |
temporally unlimited |
|
Pandemic |
spatially unlimited |
temporally limited |
Known pandemics and epidemics
Every year, the seasonal influenza virus – always in a slightly different form – causes outbreaks of illness, usually limited to specific regions. These flu epidemics are sometimes more and sometimes less severe in different regions.
Closely related to the currently rampant SARS-CoV-2 coronavirus is the SARS virus (Sars-CoV). It triggered a pandemic in 2002/2003: Around 8,000 people worldwide were infected with the then novel pathogen. 774 people died from the “severe acute respiratory syndrome” (SARS) caused by the pathogen.
Whether the clustered occurrence of an infectious disease is called a pandemic does not depend on how many people become infected with the pathogen in question, subsequently fall ill and possibly die from it!
The HIV virus first appeared in the early 1980s. Initially, HIV infections caused a “delayed” epidemic (tardivepidemic) before they eventually began to spread pandemically – an epidemic became a pandemic. It is now estimated that more than 33 million people worldwide are infected with the AIDS pathogen. The number of deaths due to AIDS is estimated at 1.8 million per year.
The warm, humid climate and often poor hygiene conditions in tropical-subtropical countries also make it easy for many other pathogens. In Africa, for example, small-scale Ebola epidemics occur time and again. In principle, however, pandemics and epidemics can also occur in other climatic regions and under otherwise high standards of hygiene. The latest evidence of this is the Covid 19 pandemic.
