Difference between Pandemic, Endemic and Epidemic Disease

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Difference Between Pandemic, Endemic, And Epidemic Disease

Infectious diseases are spread by either bacterial or viral agents and are ever-present in society. The spread and rate of new cases can be classified as

Sporadic: used to describe when a disease is happening infrequently and irregularly.

Endemic: something that’s a constant presence in a geographic area. For instance, there are tropical parts of the world where the mosquito-borne infection malaria is endemic.
Epidemic: which is a sudden increase in the number of cases and is more than what’s expected for an area.
Pandemic: A pandemic is used to describe a disease that has spread across many countries and affects a large number of people.

Endemic

It is used to describe a disease that is present at an approximately constant level within a society or country.

Each country may have a disease that is unique, for example Varicella, more commonly known as chickenpox in the UK, Malaria is another infectious disease that is endemic to Africa.

Epidemic

The term epidemic is not just used with infectious diseases. It is also used with any scenario that leads to a detrimental rise of health risks within a society. eg.

The rise in obesity globally (often described as an “obesity epidemic”). Over the last 3 decades, the United States has seen an increase in the number of people who have a BMI higher than the recommended average.

When the term epidemic is used in connection with infectious diseases it is due to the sudden rise of cases usually resulting from a new infectious agent or a change in an existing agent, for example:

An agent moving between host populations, for example moving from animals to humans (zoonotic diseases)
A genetic change (mutation) in the infectious agent, eg bacteria, virus, fungi or parasite
Introduction of new pathogens to a host population

Epidemics can follow predictable patterns and these trends are often used to monitor, predict and control the spread of the infection. A typical example of this is seasonal flu.

Pandemic

Once an epidemic becomes global and affects a large percent of the population it becomes known as a pandemic. The terms pandemic and epidemic are used to describe the rate and distance of the spread of the disease and not the severity of the disease. Significant features of a pandemic are listed below:

Affects a wider geographical area, often global

Infects a very large number of people
Often caused by a new virus or a new strain of a virus that has been dormant for many years.
Spreads quickly in humans as there is little to no existing immunity
Can cause a high number of deaths
Because of the need to control the spread of the disease, there is often social disruption, unrest and economic loss

Some previous examples of pandemics include

The Spanish flu (H1N1 virus) of 1918. About 500 million people – a third of the population around the globe – were sick from the Spanish flu. A total of 50 million people or more died from it around the world.
In 1968, there was a pandemic caused by an influenza A (H3N2) virus that killed a million people worldwide.
In 2009, a pandemic of swine flu killed 14,286 people worldwide. Although the WHO declared an end to the H1N1 pandemic in August 2010, the virus still circulates seasonally during flu season.
In history there have been a number of devastating pandemics including smallpox, tuberculosis and the black death, which killed more than 75million people way back in 1350.

Stages of a Pandemic

The WHO has identified six phases that it follows before declaring a pandemic. Phase 1 represents a low risk and phase 6 is a full-blown pandemic, you can see the phases below:

Phase 1 – a virus is seen in animals but has not been shown to infections in humans

Phase 2 – a known animal virus has caused an infection in humans
Phase 3 – scattered or isolated incidence of cases or small clusters of the disease occurring in humans; possible cases of human-to-human transmission but not at a level to cause community-level outbreaks
Phase 4 – human to human transmission at a rate that causes an outbreak in communities
Phase 5 – the spread of the disease between humans is now evident in more than one country
Phase 6 – community-level outbreaks are in at least one additional country other than that seen in phase 5.

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