When a virus replicates, it can change very slightly every time. This change (or mutation) is usually so small that it has almost no effect on how ill you become and how the virus spreads. Sometimes a change does cause a virus to behave differently, for example allowing it to spread more easily. RIVM National Institute for Public Health and the Environment closely monitors changes in the coronavirus SARS-CoV-2 in the Netherlands and the consequences of those changes. 

It is known that viruses change frequently. There are already thousands of variants of the coronavirus SARS-CoV-2. RIVM National Institute for Public Health and the Environment is conducting laboratory research to see which variants are present in the Netherlands and what that means for the spread of the virus in the Netherlands. This is known as pathogen surveillance. It is mainly important to know whether the variants that are circulating also have new characteristics that pose additional risks. For example if they are more easily transmitted, if they make people more ill, or if the virus variants do not respond as well to vaccination.

Variants in the Netherlands

The World Health Organization (WHO) and the European Centre for Disease prevention and Control (ECDC) publish weekly overviews of Variants of Concern and Variants of Interest. These variants are carefully monitored and mapped due to their (potential) high-risk characteristics and degree of spread. RIVM is following the recommendations of the WHO and the ECDC in this respect, and advising these bodies based on its own findings. 

During pathogen surveillance, randomly selected samples are examined every week. These samples come from people who tested positive for the virus in a GGD test lane or a hospital in the Netherlands. In 2020, it started with dozens of samples every week. More and more laboratories joined the efforts, and RIVM now analyses about 1800 samples a week, about 1500 of those from the samples randomly selected in the context of pathogen surveillance.

14-01-2022 | 5:30 PM: The pathogen surveillance data has been updated until 12 January 2022. This data will be updated as soon as possible.

Results pathogen surveillance

The table below shows the pathogen surveillance results for the Variants of Concern and Variants of Interest identified by WHO and ECDC.  The total number of samples analysed in the context of pathogen surveillance includes not only the variants in this table, but all other variants as well. These results show the samples that were successfully analysed. The samples that were not successfully analysed are not shown in this table. The underlying data is public. The full data set also contains the data on the current Variants under Monitoring.

Weeknumber Total 2021/52 2021/51 2021/50 2021/49 2021/48 2021/47 2021/46 2021/45 2020/49 to 2021/44
Designation 76838 611 1489 1830 1877 1896 1927 1894 1803 63511
Alpha (B.1.1.7) 26267 0 0 0 0 0 0 0 0 26267
Beta (B.1.351)  439 0 0 0 0 0 0 0 0 439
Gamma (P.1)  384 0 0 0 0 0 0 0 0 384
Delta (B.1.617.2) 43486 254 1061 1663 1848 1885 1923 1894 1803 31155
AY.4.2* 463 3 50 58 60 50 50 44 42 106
Mu (B.1.621) 46 0 0 0 0 0 0 0 0 46
Lambda (C.37) 11 0 0 0 0 0 0 0 0 11
Omikron (B.1.1.529) 994 357 428 166 28 11 4 0 0 0

Download the table of virus variants

Pathogen surveillance data is updated weekly. New reports may be added up to and including week 50 of 2021 from the submissions provided by the (current and new) laboratories participating in pathogen surveillance. In any case, the figures for week 51 are not yet complete. In addition, numbers per week may differ from previous publications due to updates of sample collection dates or reclassification of the sample in the registration system (source and contact tracing instead of random sampling). These weekly figures are updated retroactively. 

As of 26 November 2021, ECDC escalated B.1.1.529 variant of interest (VOI) and is therefore included in the table from now on. B.1.616, B.1.620, B.1.427/429 (Epsilon), P.3 (Theta), B.1.525 (Eta), B.1.526 (Iota), B.1.617.1 (Kappa) and P.2 (Zeta) are de-escalated and removed by the WHO and ECDC.

*The numbers for AY.4.2 are also included in the total number for the Delta variant (B.1.617.2)

Graph variants

grafiek verdeling Delta Omikron 21 januari 2022

The graph shows the delta variant and the omicron variant of SARS-CoV-2.

Difference in proteins

So far, the main difference in the virus variants and the B.1.525 variant seems to be the changes in the ‘spike protein’, the lines bristling out from the coronavirus. The proteins of these virus variants may be able to attach themselves to human cells more effectively. 

Reproduction number R: how fast is the virus spreading?

When assessing the risks of a virus variant, it is important to know how contagious the variant is and how easily it spreads. Once there are more cases involving a specific virus variant, RIVM National Institute for Public Health and the Environment can calculate the reproduction number for that variant. The R number represents the number of people infected by someone who has the virus. It shows how quickly a specific variant can spread. 

Alpha variant, B.1.1.7

The Alpha variant of the coronavirus, first found in the UK, was also detected in the Netherlands in December 2020. The Alpha variant then became the dominant strain in the Netherlands, supplanting the former variant of the virus. In summer 2021, the Alpha variant was ‘pushed out’ by the more contagious Delta variant.

Beta variant, B.1.351

The Beta variant of the coronavirus, first found in South Africa, was detected in the Netherlands in early January 2021. This variant of the virus, like the Alpha variant, also appears to be more contagious than the variant that had been dominant in the Netherlands until that point. The Beta variant is no longer detected in pathogen surveillance.

Gamma variant, P.1

The P.1 Gamma variant of the coronavirus was found mainly in outbreaks in and around Manaus, the capital of the Brazilian state of Amazonas. It is not yet clear whether the course of illness is different for this variant. Among other mutations, the variant has three changes in the spike protein, the lines bristling out from the coronavirus, that are considered cause for concern. These three changes are almost identical to the changes in the Beta variant. The immune response due to vaccination or due to previous infection with the virus may possibly be less effective against this variant.  The P.1 Gamma variant is currently no longer detected in pathogen surveillance.

Delta variant, B.1.617.2

The B.1.617.2 variant of the coronavirus was first found in October 2020 in India. In summer 2021, the Delta variant (B.1.617.2) replaced the Alpha variant as the dominant strain in the Netherlands. All the infections that have been typed in the context of pathogen surveillance in the Netherlands currently involve the Delta variant. The same trend is occurring all over the world. The Delta variant is much more contagious than the Alpha variant.
The COVID-19 vaccines are effective in preventing hospital and ICU admissions, even against the Delta variant.

Omicron variant B.1.1.529

The first cases involving the Omicron variant (B.1.1.529) of the coronavirus SARS-CoV-2 were reported in South Africa at the end of November 2021. The percentage of cases involving the Omicron variant is rising rapidly around the world, including in the Netherlands. The rapid spread of the Omicron variant may lead to a high peak in hospital and ICU admissions – a peak that could significantly exceed care capacity. To prevent this, the Outbreak Management Team (OMT) recommended expanding the evening lockdown on 17 December 2021. By now, the Omicron variant is spreading so fast that it will probably become the most common and dominant variant in the Netherlands before the end of the year. Similar to other variants, the small changes (mutations) in this new variant are seen mainly in the lines bristling out from the coronavirus: the spike protein. A striking feature of this variant is that it has an unusually large number of mutations in the spike protein. That includes a number of mutations at locations that alter the properties of the virus.

Initial research shows that vaccine effectiveness against infection without booster vaccination is considerably lower compared to the Delta variant. People can get the Omicron variant of the virus, even if they have had the coronavirus before or have already been vaccinated. Protection against infection with the Omicron variant increases significantly after a booster jab. It is not yet known whether the virus variant also causes people to become more seriously ill from a coronavirus infection.

The Omicron variant is detected by the PCR tests used in the Netherlands for COVID-19 testing. However, like the Alpha variant, the Omicron variant produces a non-standard result on a special PCR test based on detecting the presence of the spike protein. This test is not generally used in diagnostics in the Netherlands. However, this special test may be used to track the Omicron variant in pathogen surveillance. The Omicron variant has been designated as a Variant of Concern by WHO and ECDC.

Read more about the Omicron variant

Prevent infection with variants

 What can you do to prevent the virus from spreading? The recommendations are the same for all variants of the coronavirus: if you have symptoms, stay home and get tested by the GGD, keep distancing, and wash your hands regularly.

Frequently asked questions

How can you tell which variant of the coronavirus someone has?

If you test positive for COVID-19, the test results do not tell you which coronavirus variant you have. When analysing a COVID-19 test, a laboratory technician cannot see which variant of the coronavirus SARS-CoV-2 caused the infection. This requires further research, known as sequencing. This means further investigation of the virus sample that was taken with a cotton swab in the nose and throat. Sequencing looks at the building blocks of the virus. By looking at how the virus is constructed, it is possible to recognise characteristic ‘building blocks’ of a variant. Sequencing is performed on random samples in the context of pathogen surveillance

What is the AY.4.2 variant and what do we know about this virus variant? 

The AY.4.2 variant is a sub-variant of the Delta variant of the coronavirus SARS-CoV-2. This variant is found in many European countries. The variant is identified based on three mutations. This type has been found occasionally in pathogen surveillance in the Netherlands from August 2021 on; over the past few weeks, it seems to be very slowly increasing. In mid-November 2021, the European Centre for Disease Prevention and Control (ECDC) escalated its designation to Variant of Interest. These variants are carefully monitored and mapped due to their (potential) high-risk characteristics and degree of spread. 

Indications are that the AY.4.2 variant is also slowly gaining ground in England. In the Netherlands, it is currently responsible for about 15% of SARS-CoV-2 infections, with regional differences. However, not much is known about this variant at this time. For example, we do not know how transmissible the variant is compared to other variants. There are no indications that the current vaccines will not offer effective protection against this variant of the virus.

Why has the Omicron variant not yet been found in the national pathogen surveillance?

This is because pathogen surveillance analyses a random sample of specimens from 31 different laboratories in the Netherlands. Random sampling provides a representative overview, but never achieves a comprehensive analysis. Most infections involving the Omicron variant that have been found so far in the Netherlands were detected in the context of targeted investigation of people with a history of travel to southern Africa.   Moreover, the first indications that the Omicron variant was present in the Netherlands were only found on 24 November 2021. That is too recent to determine widespread occurrence of this variant in the current sampling. The variant was not found in the samples up to and including the week of 15-22 November 2021. This means that the Omicron variant is not circulating widely in the Netherlands at this time.