Corona: Pandemic, epidemic, endemic – what does that mean?

The SARS-CoV-2 coronavirus spread from China worldwide since the end of 2019. At first, the infections seemed limited to individual countries; there was talk of a coronavirus epidemic. Only about ten weeks after the first coronavirus cases became known, the World Health Organization (WHO) classified the spread of the coronavirus as a pandemic. The disease COVID-19 caused by SARS-CoV-2 soon spread to all continents. Experts assume that the pandemic will develop into an endemic. But when exactly does one speak of a pandemic? How is it different from the epidemic? And what is the difference to an endemic? Find out below what these terms are all about and what they mean concerning Corona.

What is a pandemic?

If a disease spreads uncontrollably across numerous countries and continents, it is called a pandemic. According to the WHO, a pandemic is when the world’s population is exposed to a pathogen for a certain period.

The term pandemic does not explain how contagious or dangerous such an infectious disease is. The spread of the SARS-CoV-2 coronavirus has been classified as a pandemic by the WHO. This made it clear that COVID-19 is affecting people worldwide.

 

 

How does a pandemic arise?

A prerequisite for the emergence of a pandemic is that the disease can be transmitted from person to person. This applies to the current case of the COVID-19 pandemic. The SARS-CoV-2 virus spreads quickly in the population via droplet infection.

Due to the high level of global mobility, the virus quickly spread across borders and worldwide. Initially limited to China, the former coronavirus epidemic expanded into the coronavirus pandemic.

How does a pandemic develop?

Pandemics do not develop linearly, i.e. the number of infections does not increase evenly from one day to the next. Instead, one speaks of an exponential growth in the number of infections. Such infections often begin harmlessly with low infection numbers, increasing sharply and quickly. You can imagine the beginning of a pandemic like this:

• One person infected with one pathogen infects two people.
• These two people, in turn, infect two people each.
• In the meantime, seven people have already been infected, of whom the latest four infect two people each, so that 15 people are already carrying the pathogen – and so on.

If you start a so-called exponential growth model with an initial number of infected people of 6,000 (approximate number of SARS-CoV-2 infected people in Germany in mid-March 2020) and assume that the infections will double every three days, then infect more than 100,000 people within two weeks.

This is precisely where the various measures to contain the coronavirus pandemic come in: vaccinations, hygiene measures, and contact restrictions intended to reduce the number of new infections, flatten the growth curve, and thus relieve the healthcare system.

How many people an infected person infects on average varies from pathogen to pathogen. This number is also known as the reproduction number or R-value. With SARS-CoV-2, it can be observed that this number of reproductions can change in the course of virus mutations. For example, the delta variant has a much higher R-value than the archetype of the coronavirus. You can find detailed information about the R-value here.

 

What to do in the event of an impending pandemic?

Germany has the National Pandemic Plan (NPP) as a guideline for dealing with a possible pandemic. This aims to slow the spread of disease, keep the number of illnesses and deaths as low as possible, and ensure the care of sick people.

The pandemic plan shows the existing structures and the measures necessary during a pandemic. It presents the current scientific basis for pandemic management provided by the Robert Koch Institute (RKI). The NPP can be viewed as an emergency plan during a pandemic.

What pandemics have there been in the past?

In recent years, the WHO has classified the following waves of infection that have spread worldwide as pandemics:

• Plague (1346 to 1353): The causative agent of the plague, a bacterium called Yersinia pestis, claimed around 25 million lives. The plague can be treated today thanks to antibiotics but has not yet been eradicated.
• Spanish flu (1918/1919): A variant of the H1N1 virus killed around 50 million people worldwide.
• HIV (since 1980): HIV has claimed 33 million lives to date. The disease AIDS caused by the virus can now be treated with antiviral drugs.
• SARS (2002/2003): The SARS-CoV-1 coronavirus causes respiratory diseases that have claimed the lives of around 1,000 people.
• Swine flu (2009/2010): The H1N1 virus claimed 18,000 lives; most infected had no symptoms.
• COVID-19 (since 2019): The SARS-CoV-2 coronavirus has been spreading worldwide since the end of 2019, causing numerous deaths daily.

Current information about the coronavirus

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What is an epidemic?

If the occurrence of a disease is limited in time, as in the case of a pandemic, but only occurs in a specific region, then it is called an epidemic. The term epidemic describes the temporary and only recently identified localized disease occurrence.

Epidemics have been common in the past. Tropical diseases such as dengue fever or Ebola infections are among the epidemic diseases, but polio, typhus, anthrax and the flu are also included.

The real flu – epidemic or pandemic?

Influenza waves, i.e. infections with the influenza virus (real flu), occur repeatedly. In the last hundred years, humanity has often been afflicted by influenza epidemics or pandemics.

The flu pandemics include the following flu waves:

• Spanish flu (1918/1919)
• Asia-Virus (1957-1968)
• Hong Kong Flu (1968-1970)
• Russian flu (1970s)

The 1995/1996 flu epidemic, which killed around 30,000 people in Germany alone, is one of the flu epidemics – that is, flu waves that did not have the extent and spread of the flu pandemics mentioned above.

Influenza viruses are very adaptable and are constantly changing their genetic material. As a result, you can catch and get sick with the flu more than once. That is also why the vaccine against influenza has to be adjusted every year, and a new vaccination is necessary to build up sufficient protection against the influenza viruses.

What is endemic?

An endemic is when a persistent disease only occurs in a specific region. In this case, the pathogens are constantly present and cannot be eliminated by vaccination or treating the sick person.

An excellent example of a so-called endemic disease is malaria in tropical countries. The reason for the spatial limitation to warm and humid areas can be found in the path of transmission of the pathogen. The unicellular parasite Plasmodium is transmitted by female Anopheles mosquitoes living in water-rich, warm regions. The mosquitoes have the pathogen in their saliva and share it during the biting process. Since these mosquitoes are not found in other areas, the spread of malaria is also regionally limited.

Tick-borne encephalitis (FSME), which ticks can transmit, is also an example of a disease that only occurs in a few areas – primarily in southern Germany but also in Switzerland and Austria. Here, only regions are affected in which ticks occur that harbour the pathogen, a virus. These areas are also known as endemic areas.

Childhood diseases such as measles and mumps are also endemic because they usually occur frequently and locally.

 

Will Corona become endemic?

According to experts, the coronavirus could also develop into an endemic. They assume vaccination cannot completely eradicate the virus, and herd immunity now seems unlikely. Corona will continue to accompany us in the future and will likely cause new waves of infection.

However, most people’s immune systems will likely be exposed to the coronavirus through vaccination or infection. Then, the virus could lose some of its danger since this elemental immunity could mean that waves of infection would no longer result in so many seriously ill people.

A high vaccination rate could accelerate the transition from pandemic to endemic, but emerging virus variants could also delay it. According to experts, worldwide immunization of the population is essential to increase elemental immunity and prevent the occurrence of new virus mutations.