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How do we know what coronavirus variants there are?

By nature, a virus keeps on changing just a little bit. Sometimes a change can cause a virus to behave differently or enable it to spread more easily. This is why new variants of coronavirus are closely monitored. But how do we keep track of the different variants and how often they occur?

RIVM investigates what coronavirus variants are circulating.

This article explains the importance of research into variants of the coronavirus and explains the figures that are shown on the dashboard.

One of the characteristics of a virus is that it tries to infect as many people as possible, which is why it replicates itself so quickly. Each time the virus replicates itself, it is possible for it to change slightly. Usually this change – known as a mutation – is so small that it has no influence on how the virus spreads, or how ill it could make you. However, it is possible that a mutation causes the virus to behave differently and become more infectious, or even cause more severe illness, so variants have to be monitored closely.

Tracking variants
In the Netherlands, the National Institute for Public Health and the Environment (RIVM) investigates what coronavirus variants are circulating, and whether and how the virus is changing. This is known as genomic pathogen surveillance. As part of this research a number of laboratories around the Netherlands examine around 1,500 randomly selected positive test samples a week. RIVM carries out the pathogen surveillance jointly with these laboratories and Erasmus MC. In the laboratory, the building blocks of the virus are mapped out and compared with other samples. This enables RIVM to see how the virus changes. It also looks at how the different variants spread.

Extensive research
Pathogen surveillance involves specialists from a number of fields and highly advanced equipment. The laboratory analyses are more complicated and take more time than an analysis of a PCR test for coronavirus. The research also provides other valuable information. RIVM uses data from this research in mathematical models to predict the course of the epidemic and calculate the effects of measures.

Different variants
There are already thousands of variants of novel coronavirus (SARS-CoV-2). The European Centre for Disease Prevention and Control (ECDC) and the World Health Organization (WHO) have designated key variants as variants of concern or variants of interest. A variant is labelled a variant of concern if it is more infectious, causes more severe illness or if vaccines are less effective against it. A variant of interest is one that has been traced to multiple cases in a specific situation or cluster, or one that has been found in several countries.

It is important to know if the circulating variants have any new properties that could pose additional risks. Fortunately, the vaccines that are used in the Netherlands protect against the variants that we currently know about.

Which variants do we have in the Netherlands?
The table on the dashboard shows the variants of concern and interest in the Netherlands. Specifically, it shows the share of each variant among the samples analysed in pathogen surveillance each week. This shows which variant occurs most often. The variants are referred to here by the names given to them by WHO. For example, the Alpha variant was initially called the UK variant because it was first found there.

Variants of the coronavirus


One variant supplants another
The original SARS-CoV-2 virus that went around the world in the spring of 2020, and which also infected the Netherlands, is now hardly ever found in samples taken in the Netherlands. In the spring of 2021 the Alpha variant was predominant, as can be seen in the graph below. Here you can clearly see that the most contagious variant will gain the upper hand over time. Below, the Alpha variant is compared with the original SARS-CoV-2 virus. The graph on the dashboard shows only those variants that pose the biggest potential threat, i.e. the variants of concern.

The graph on the dashboard shows what percentage of samples analysed each week are of a particular variant, as well as the total number of samples.

The graph on the dashboard shows what percentage of samples analysed each week are of a particular variant, as well as the total number of samples.