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One of the general characteristics of viruses is their genetic instability meaning that they prone to change from one generation to another, and newer and newer virus variants occur as a result of novel genetic mutations. The mutation rate of SARS-CoV-2 virus is slightly lower compared to that of other RNA-viruses, such as the influenza virus.


Some genetic mutations do not cause significant alterations in the viral characteristics. These variants are not registered epidemiologically, since the high incidence of mutations would make it impossible to follow all of them.


Genetic mutations in viruses might have an impact on:


  • pathogenicity, and transmission rate,
  • the symptoms and severity of the disease they cause
  • the duration of the infection and the disease course,
  • the diagnostic method that can detect the infection,
  • the efficacy of vaccination and medications.


In the following section, you can read a brief description on SARS-CoV-2 virus and its main variants, accounting for the COVID-19 pandemic.


Delta variant: Things you should know

The delta variant has been present worldwide and spreads at a higher rate than the original form and the previous variants of SARS-CoV-2.


The most important characteristics of the delta variant:


  • increased pathogenicity: its pathogenicity is more than twice as high compared to other variants, which means that an infected individual infects twice as much people (average of 6 people), as they did before in the earlier waves of COVID-19,
  • shorter incubation period (average of 4 days),
  • more severe symptoms: compared to other variants, there is a higher rate of hospitalizations (people who need hospital treatment) among the infected individuals (in the unvaccinated population),
  • differing symptoms: loss of taste and smell have become rare, while respiratory- and cold-like symptoms have become more common (headache, sore throat, runny nose, sneezing, subfebrility, fatigue, digestive problems, redness of the eye and increased tearing).


Another significant difference is that the fully vaccinated people tend to spread the delta variant easier, than other variants – although, the time of infection and while the infected individual carries and spreads the virus is shorter in the vaccinated population.


The currently available COVID-19 vaccines are effective against the delta variant, too. Vaccines do not protect against the infection itself, but they protect against developing a disease with more severe symptoms, and decrease the need for hospitalization and the number of deaths.


Omicron variant: things you should know

At the end of 2021, the omicron variant has been recorded in the most countries of the world, and the number of COVID-19 diseases spread by the omicron has also been on an increase. There are certain regions where the omicron is the dominant SARS-CoV-2 variant.


The most important characteristics of the omicron variant:


  • several mutations in the spike protein: several mutations are present in the omicron variant (the most important is within the genes coding the spike protein – among the 30 amino acids coding the spike protein, 15 have changed) – its exact effect on the vaccinated individuals is unkown yet, but data have been continuously collected and analyzed regarding this topic,
  • increased pathogenicity: the omicron variant’s pathogenicity is 36% higher than that of the delta. One reason behind this phenomenon might be that as a result of the high mutation rate, this variant may break through acquired immunity more easily,
  • milder symptoms: the proportion of hospitalized individuals are lower compared that of with the delta variant (but the high number of infected individuals still accounts for a great burden on the health care system),
  • high risk for re-infections: the defense mechanisms of the immune system are likely to be less persistent.


The currently available COVID-19 vaccines are effective against the omicron variant, too. Vaccines do not protect against the infection itself, but they protect against developing a disease with more severe symptoms and decrease the need for hospitalization and the number of deaths.


The nomenclature of COVID-19 variants

The WHO uses simple, easy-to-remember and easy-to-pronounce names in the nomenclature of the genetic mutations of the COVID-19.


Since the virus continuously changes, the number of the newly occurring variants are untraceably high, thereby “common, public names” are only given to those variants of epidemiological importance. These names are used in public communication and in the different means of media in order to make communication plain and simple.


The original variant (code)names can be found in the following databases:


  • PANGO – The Pango nomenclature was established for the identification of the coronavirus variants of epidemiological importance. This database is less scientific, it is much more illustrative – the spread of the virus is visualized on maps.
  • GISAID (Global Initiative On Sharing Avian Influenza Data) – A scientific resource that enables open access to the genomic data of influenza viruses and coronaviruses that account for the COVID-19 pandemic. Currently millions of virus variants are listed in the database.
  • Nextstrain – This is a project with open source code, with which the genomic data of distinct pathogens can be analyzed. It organizes systematically the publicly available data and provides effective analytic and visualization tools for the public. Its purpose is to foster the understanding of the epidemiological importance of the viruses.


Scientific names are hard to pronounce and recall, and easy to miss. Therefore, naming the different virus variants based on their place of identification has become popular, but this nomenclature is stigmatizing. To avoid this, the WHO has come up with the idea of creating a nomenclature of phantasy names (currently the elements of the Greek alphabet are being used), and national authorities, the press and the citizens are also expected to use this nomenclature.


However, this nomenclature does not substitute the persisting scientific (code)names, since these names code for important scientific information as well, and they are used in research. 


A detailed synthesis of the variants

Our purpose is to present the variants of global epidemiological importance, of which the following statements are true:


  • high pathogenicity,
  • the course of the disease caused by the virus has become more severe compared to that caused by the original variant (increase in number of deaths and number of hospitalizations),
  • the defense mechanisms of the acquired immune system (produced by vaccination or prior infection) is significantly weaker against the new variant,
  • decrease in efficacy of treatment or vaccination,
  • decrease in efficacy of diagnostic tools (the new variant cannot always be detected with the previous diagnostic tests).




Place of identification






United Kingdom

much faster

more severe





potentially faster

not more severe




Japan, Brazil


not more severe





much faster

potentially more severe






likely milder course



The emergence of novel virus variants with more dangerous features might lead to the introduction of new or stricter safety measures (mask wearing, organization and participation in music and dance events, curfew, etc. – the extent of the measures usually correlate with the potential threat the new variants pose on the population). Furthermore, the development of novel diagnostic methods, medical treatments or vaccines might be necessary as well.


There are several variants which are being tracked and are suspected to develop greater importance in the future.


Dangerous characteristic features include:


  • genetic mutations that potentially changes certain features of the virus (e.g., pathogenicity, the severity of the disease they cause, and the efficacy of the diagnostic methods and medical treatments),
  • their transmission is easier, or they develop multiple infection foci,
  • other epidemiological data suggest that the variant poses or will pose an epidemiological risk globally in the future.




Place of identification








These variants have been continuously monitored so that protective measures can be taken early. For further information on the symptoms of COVID-19 infection and the course of action in case of an infection, read the applicable articles:


General information on COVID-19 vaccines

Booster vaccination against COVID-19


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