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Current events on respiratory infections
Modified date 04-02-2026 | 16:22
The RIVM shares the latest figures on respiratory infections in the Netherlands every Wednesday.
Update February 4, 2026: Number of people with a respiratory infection is increasing, flu epidemic seems to be in sight
The share of participants in Infection Radar(external link)The number of people with respiratory complaints has increased in the past week. Some of these participants submitted a throat and nose sample to the RIVM (National Institute for Public Health and the Environment). Seasonal coronaviruses, influenza virus, and rhinovirus/enterovirus* were the most common viruses in these samples.
In patients who visited their GP with respiratory complaints and had a sample taken, the influenza virus was the most frequently detected virus over the past three weeks. Last week, influenza virus was found in 24 (37%) of the 65 samples. The proportion of RS virus was slightly higher last week than the previous week (8% versus 7%). In the figures from laboratories in the Netherlands (the Virological Weekly Reports), influenza virus and RS virus were detected most frequently last week. Other viruses, including rhinovirus, seasonal coronaviruses, and human metapneumovirus (hMPV), were also detected in both GP and laboratory samples.
The number of IC(Intensive care)-admissions due to respiratory complaints ( SARI surveillance ) decreased further in the past week.
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Variants of the flu virus
Modified date 05-02-2026 | 15:01
The RIVM, Erasmus MC(Erasmus University Medical Center)Rotterdam and Nivel together form the National Influenza Centre (NIC). One of the tasks of the NIC(National Influenza Center)The goal is to analyze which influenza virus variants are causing infections in the Netherlands. This page explains how the NIC conducts this and which influenza virus variants are currently circulating.
Analysis of influenza virus variants
The NIC(National Influenza Center)analyzes which genetic variants of the influenza virus are circulating and what their properties are. This knowledge helps determine, among other things, whether current vaccines are compatible with the viruses currently circulating. It also helps determine whether currently circulating influenza viruses may be less sensitive to antiviral therapies.
The NIC analyses influenza viruses from:
Current situation: Overview of influenza virus variants for the 2025-2026 season
In recent weeks, the number of influenza viruses found each week in the Netherlands has been steadily increasing. Of the samples analyzed by the NIC in the 2025-2026 season, influenza A(H1N1)pdm09 and A(H3N2) viruses were primarily found in various sources, with influenza B virus still present to a very limited extent.
Changes in the hemagglutinin (HA) protein of the influenza virus may lead to other antigenic properties of the virus, such as a reduction in the immunity induced by previous infections and vaccination.
A(H1N1)pdm09 and A(H3N2) influenza viruses
Recent sequencing results show that for both the A(H1N1)pdm09 and A(H3N2) influenza viruses currently circulating, substitutions have been found in HA that could lead to an antigenic deviation compared to the viruses in the vaccine currently administered in the Netherlands. The antigenic properties of an initial subset of the Dutch A(H1N1)pdm09 and A(H3N2) viruses were mapped using reference ferret sera. The antigenic properties of A(H1N1)pdm09 viruses generally correspond well with this year's vaccine component, but A(H3N2) subclade K viruses deviate from this year's vaccine component and may therefore escape antibody recognition.
For A(H3N2) subclade K viruses, this is likely due to the amino acid substitutions S144N, N158D, I160K, and Q173R in HA. This indicates that the vaccine may provide less protection against the A(H3N2) subclade K viruses and, to a lesser extent, against the A(H1N1)pdm09 subclade D.3.1 viruses. Whether the vaccine actually provides less protection against severe disease is being closely monitored. Initial data from the United Kingdom show that protection is not yet drastically lower than in previous years. Early vaccine effectiveness measurements from the VEBIS(external link)A consortium of the RIVM and Nivel confirms early measurements from the United Kingdom. The vaccine effectiveness against A(H3N2) influenza virus, with clade K circulating dominantly, is comparable to that of previous seasons. The effectiveness against A(H1N1)pdm09 influenza virus, with increasing dominance of clade D.3.1.1, is also comparable to that of previous seasons, but somewhat lower than that against A(H3N2).
Antiviral sensitivity
Representative viruses from the various subtypes are being tested for susceptibility to antiviral agents such as oseltamivir and zanamivir. Currently circulating A(H3N2) viruses, including the aforementioned clade K, show similar susceptibility to previous variants.
Among A(H1N1)pdm09 viruses, the most common variant this season, clade D.3.1.1, has changes (substitutions) in the neuraminidase protein that can lead to reduced susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir: NA-I223V and/or NA-S247N. A large proportion of clade D.3.1.1 viruses have NA-S247N, and double mutants are also observed. The double mutant, in particular, results in reduced susceptibility.
(Source: RIVM/Erasmus MC(medical center))
(screenshots)
...
Current events on respiratory infections
Modified date 04-02-2026 | 16:22
The RIVM shares the latest figures on respiratory infections in the Netherlands every Wednesday.
Update February 4, 2026: Number of people with a respiratory infection is increasing, flu epidemic seems to be in sight
The share of participants in Infection Radar(external link)The number of people with respiratory complaints has increased in the past week. Some of these participants submitted a throat and nose sample to the RIVM (National Institute for Public Health and the Environment). Seasonal coronaviruses, influenza virus, and rhinovirus/enterovirus* were the most common viruses in these samples.
In patients who visited their GP with respiratory complaints and had a sample taken, the influenza virus was the most frequently detected virus over the past three weeks. Last week, influenza virus was found in 24 (37%) of the 65 samples. The proportion of RS virus was slightly higher last week than the previous week (8% versus 7%). In the figures from laboratories in the Netherlands (the Virological Weekly Reports), influenza virus and RS virus were detected most frequently last week. Other viruses, including rhinovirus, seasonal coronaviruses, and human metapneumovirus (hMPV), were also detected in both GP and laboratory samples.
The number of IC(Intensive care)-admissions due to respiratory complaints ( SARI surveillance ) decreased further in the past week.
...
----------------------------------------------------------------------------------------------------
Variants of the flu virus
Modified date 05-02-2026 | 15:01
The RIVM, Erasmus MC(Erasmus University Medical Center)Rotterdam and Nivel together form the National Influenza Centre (NIC). One of the tasks of the NIC(National Influenza Center)The goal is to analyze which influenza virus variants are causing infections in the Netherlands. This page explains how the NIC conducts this and which influenza virus variants are currently circulating.
Analysis of influenza virus variants
The NIC(National Influenza Center)analyzes which genetic variants of the influenza virus are circulating and what their properties are. This knowledge helps determine, among other things, whether current vaccines are compatible with the viruses currently circulating. It also helps determine whether currently circulating influenza viruses may be less sensitive to antiviral therapies.
The NIC analyses influenza viruses from:
- samples that a large number of clinical diagnostic laboratories in the Netherlands send for analysis
- samples from the Nivel GP sentinel stations of people with an acute respiratory infection
- Infection Radar samples from people in the general population with a (mild) acute respiratory infection
Current situation: Overview of influenza virus variants for the 2025-2026 season
In recent weeks, the number of influenza viruses found each week in the Netherlands has been steadily increasing. Of the samples analyzed by the NIC in the 2025-2026 season, influenza A(H1N1)pdm09 and A(H3N2) viruses were primarily found in various sources, with influenza B virus still present to a very limited extent.
- Of the genetically characterized influenza A(H1N1)pdm09 viruses, most belonged to clade 5a.2a.1 (subclades D.3.1 and D3.1.1). Subclade D3.1.1 has been predominant since week 47/2025.
- Of the genetically characterized influenza A(H3N2) viruses, most belonged to clade 2a.3a.1 (subclade K). This clade K contains several changes compared to the current vaccine (see Antigenic Characterization).
- Influenza B viruses have been sporadically occurring so far this season. A few have been genetically characterized so far, with clade V1A.3a.2 (subclade C.5.6) being the most common.
Changes in the hemagglutinin (HA) protein of the influenza virus may lead to other antigenic properties of the virus, such as a reduction in the immunity induced by previous infections and vaccination.
A(H1N1)pdm09 and A(H3N2) influenza viruses
Recent sequencing results show that for both the A(H1N1)pdm09 and A(H3N2) influenza viruses currently circulating, substitutions have been found in HA that could lead to an antigenic deviation compared to the viruses in the vaccine currently administered in the Netherlands. The antigenic properties of an initial subset of the Dutch A(H1N1)pdm09 and A(H3N2) viruses were mapped using reference ferret sera. The antigenic properties of A(H1N1)pdm09 viruses generally correspond well with this year's vaccine component, but A(H3N2) subclade K viruses deviate from this year's vaccine component and may therefore escape antibody recognition.
For A(H3N2) subclade K viruses, this is likely due to the amino acid substitutions S144N, N158D, I160K, and Q173R in HA. This indicates that the vaccine may provide less protection against the A(H3N2) subclade K viruses and, to a lesser extent, against the A(H1N1)pdm09 subclade D.3.1 viruses. Whether the vaccine actually provides less protection against severe disease is being closely monitored. Initial data from the United Kingdom show that protection is not yet drastically lower than in previous years. Early vaccine effectiveness measurements from the VEBIS(external link)A consortium of the RIVM and Nivel confirms early measurements from the United Kingdom. The vaccine effectiveness against A(H3N2) influenza virus, with clade K circulating dominantly, is comparable to that of previous seasons. The effectiveness against A(H1N1)pdm09 influenza virus, with increasing dominance of clade D.3.1.1, is also comparable to that of previous seasons, but somewhat lower than that against A(H3N2).
Antiviral sensitivity
Representative viruses from the various subtypes are being tested for susceptibility to antiviral agents such as oseltamivir and zanamivir. Currently circulating A(H3N2) viruses, including the aforementioned clade K, show similar susceptibility to previous variants.
Among A(H1N1)pdm09 viruses, the most common variant this season, clade D.3.1.1, has changes (substitutions) in the neuraminidase protein that can lead to reduced susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir: NA-I223V and/or NA-S247N. A large proportion of clade D.3.1.1 viruses have NA-S247N, and double mutants are also observed. The double mutant, in particular, results in reduced susceptibility.
(Source: RIVM/Erasmus MC(medical center))
(screenshots)
...