On this page, you can find information about the surveillance of:
- acute respiratory infections (including influenza-like illness (ILI)), also known as acute respiratory infection (ARI), including:
- children with bronchiolitis in primary care,
- pneumonia in primary care, and
- severe acute respiratory infections (SARI).
Because most respiratory infections mainly occur in winter, the numbers are presented for a respiratory season or a respiratory year. A respiratory season runs from week 40 of one year through week 20 of the following year. A respiratory year runs from week 40 of one year through week 39 of the following year. This report looks at the respiratory season 2024/2025.
Acute respiratory infection (ARI) and influenza-like illness (ILI)
Acute respiratory infections (ARIs) and influenza-like illness (ILI) are clinical syndromes that can be caused by various pathogens. The definition of ILI falls within that of ARI, but is more specifically focused on symptoms that indicate a possible infection with the influenza virus (flu). For more details on the definitions of ARI and ILI, see the background and methods document on respiratory surveillance for 2024/2025.
Peaks in week 5 of 2025
The number of reports of both ARIs and ILI reached a peak in week 5 of 2025. This is evident from the results of Infectieradar and from general practitioner (GP) data. At the time of this peak, there was increased circulation of influenza virus, RS-virus, and human seasonal coronaviruses.
Number of people with influenza-like illness has returned to pre-COVID-19-pandemic levels
The threshold for increased ILI activity in GPs, set at 5.3 per 10,000 inhabitants per week, was exceeded from week 3 to week 9 of 2025. During the peak in week 5, the ILI incidence was 10.5 per 10,000 inhabitants. This is higher than measured in the past 5 seasons, but within the usual values of the five respiratory seasons before the COVID-19 pandemic (2014/2015 through 2018/2019).
Viruses in people with respiratory infections
Among Infectieradar participants with self-reported ARI, mainly rhinovirus/enterovirus and human seasonal coronaviruses were found during the respiratory season 2024/2025. During the peak (week 5 of 2025), influenza virus and human seasonal coronaviruses were the most frequently found viruses.
In specimens from the Nivel Primary Care Database, from both ARI (including ILI) patients and ILI patients, influenza virus and rhinovirus were most often found during the respiratory season 2024/2025. In weeks 2 through 7, around the peak of GP visits for ILI and ARI, mainly influenza virus was found in these patients. In the GP specimens, little SARS-CoV-2 was found throughout the entire respiratory season 2024/2025. SARS-CoV-2 was found relatively more often in patients aged 15 years and older than in younger patients. RS-virus and adenovirus, on the other hand, were more frequently found in the younger age groups (under 15 years old).
Influenza virus and RS-virus were found relatively more often in the specimens from the Nivel Primary Care Database than in the self-test specimens from Infectieradar, but the periods when these viruses were most frequently found were similar for both surveillance systems.
Number of GP visits for respiratory infections lower than last year
During the respiratory season 2024/2025, the total number of people who visited a GP because of an ARI was lower than in the previous season 2023/2024. The number of people with an ARI or with ILI at the GP in 2024/2025 was highest in the youngest age group (0-4 years). For this age group, the number of GP visits was also lower than in the previous season. In 2024/2025, there were two peaks in the number of 0-4 year olds visiting the GP with an ARI: in week 51 of 2024 and in weeks 3 and 4 of 2025. The first peak was not seen in the older age groups. This is probably related to the circulation of RS-virus, a virus that mostly causes symptoms in young children. Data from laboratories show that this virus circulated most around week 51. The second peak in weeks 3 and 4 was also seen in the older age groups. This peak is probably related to the circulation of the influenza virus.
ARI en IAZ - 1 ARI (incl ILI) Infectieradar
Skip chart Figure 1. Weekly incidence of self-reported acute respiratory infections (including influenza-like illness) per 10,000 people participating in Infectieradar, from week 40 of 2020 through week 20 of 2025. (Source: Infectieradar, RIVM) and go to datatableARI en IAZ - 2 ARI virologie in Infectieradar
Skip chart Figure 2. Respiratory viruses found in specimens taken by Infectieradar participants with an acute respiratory infection (including influenza-like illness), as a percentage of the total number of specimens, per week, from week 40 of 2024 through week 20 of 2025. (Source: Infectieradar, RIVM) and go to datatableARI en IAZ - 3 ARI virologie leeftijden in Infectieradar
Skip chart Figure 3. Respiratory viruses found in self-test specimens taken by Infectieradar participants with an acute respiratory infection (including influenza-like illness), as a percentage of the total number of specimens, per age group*, from week 40 of 2024 through week 20 of 2025. (Source: Infectieradar, RIVM) and go to datatableFootnote: The line in the graph represents the total number of specimens tested. A specimen can test positive for multiple viruses. As a result, the stacked percentages in the graph may indicate a higher percentage of positive specimens than the actual percentage of positive specimens.
* Participation in Infectieradar is only possible for people aged 16 years and older. Therefore, the age group <20 years contains relatively few specimens.
ARI en IAZ - 4 ARI huisarts cumulatief
Skip chart Figure 4. Total number of people who visited the general practitioner due to an acute respiratory infection (including influenza-like illness) per 10,000 inhabitants, during the respiratory season (week 40 through week 20) from 2015/2016 through 2024/2025 and outside the respiratory season (week 21 through week 39) from 2015/2016 through 2023/2024. (Source: Nivel Primary Care Database) and go to datatableFootnote: Starting from this report, the diagnosis code for SARS-CoV-2 (COVID-19), R83.03, has been included in the definition of acute respiratory infection (ARI) from January 2021 onwards. The reported numbers of people with an ARI at the general practitioner during the respiratory seasons 2020/2021 and 2021/2022 are therefore slightly higher than reported last year.
ARI en IAZ - 5 ARI huisarts per week
Skip chart Figure 5. Weekly number of general practitioner visits by patients with an acute respiratory infection (including influenza-like illness) per 10,000 inhabitants, from week 40 of 2020 through week 20 of 2025. (Source: Nivel Primary Care Database) and go to datatableFootnote: Starting from this report, the diagnosis code for SARS-CoV-2 (COVID-19), R83.03, has been included in the definition of acute respiratory infection (ARI) from January 2021 onwards. The reported numbers of people with an ARI at the general practitioner during the respiratory seasons 2020/2021 and 2021/2022 are therefore slightly higher than reported last year.
ARI en IAZ - 6 ARI huisarts per leeftijdsgroep per seizoen
Skip chart Figure 6. Total number of general practitioner visits by patients with an acute respiratory infection (including influenza-like illness) for the respiratory seasons (week 40 through week 20) from 2015/2016 through 2024/2025 per 10,000 inhabitants per age group. (Source: Nivel Primary Care Database) and go to datatableFootnote: Starting from this report, the diagnosis code for SARS-CoV-2 (COVID-19), R83.03, has been included in the definition of acute respiratory infection (ARI) from January 2021 onwards. The reported numbers of people with an ARI at the general practitioner during the respiratory seasons 2020/2021 and 2021/2022 are therefore slightly higher than reported last year.
ARI en IAZ - 7 ARI huisarts per week leeftijd
Skip chart Figure 7. Weekly number of general practitioner visits by patients with an acute respiratory infection (including influenza-like illness) per 10,000 inhabitants, per age group, from week 40 of 2024 through week 20 of 2025. (Source: Nivel Primary Care Registrations) and go to datatableFootnote: Starting from this report, the diagnosis code for SARS-CoV-2 (COVID-19), R83.03, has been included in the definition of acute respiratory infection (ARI) from January 2021 onwards. The reported numbers of people with an ARI at the general practitioner during the respiratory seasons 2020/2021 and 2021/2022 are therefore slightly higher than reported last year.
ARI en IAZ - 8 ARI virologie NPS
Skip chart Figuur 8. Percentage of specimens from patients who visited the general practitioner due to an acute respiratory infection (including influenza-like illness), testing positive for a respiratory virus during the respiratory season (week 40 of 2023 through week 20 of 2024), per week. (Sources: Nivel Primary Care Database and NIC location RIVM) and go to datatableFootnote: The line in the graph represents the total number of specimens tested. A specimen can test positive for multiple viruses. As a result, the stacked percentages in the graph may indicate a higher percentage of positive specimens than the actual percentage of positive specimens.
ARI en IAZ - 9 ARI virologie NPS leeftijd
Skip chart Figure 9. Percentage of specimens from patients who visited the general practitioner due to an acute respiratory infection (including influenza-like illness), testing positive for a respiratory virus from week 40 of 2024 through week 20 of 2025, per age group. (Sources: Nivel Primary Care Database and NIC location RIVM) and go to datatableFootnote: The line in the graph represents the total number of specimens tested. A specimen can test positive for multiple viruses. As a result, the stacked percentages in the graph may indicate a higher percentage of positive specimens than the actual percentage of positive specimens.
ARI en IAZ - 13 IAZ virologie NPS
Skip chart Figure 13. Percentage of specimens from patients with influenza-like illness at the general practitioner, testing positive for a respiratory virus from week 40 of 2024 through week 20 of 2025, per week. (Sources: Nivel Primary Care Database and NIC location RIVM) and go to datatableFootnote: The line in the graph represents the total number of specimens tested. A specimen can test positive for multiple viruses. As a result, the stacked percentages in the graph may indicate a higher percentage of positive specimens than the actual percentage of positive specimens.
ARI en IAZ - 14 IAZ cumulatief leeftijd
Skip chart Total incidence of influenza-like illness at the general practitioner within the respiratory season (week 40 through week 20), per season from 2015/2016 through 2024/2025, per 10,000 inhabitants. (Source: Nivel Primary Care Database) and go to datatableChildren with bronchiolitis in primary care
Bronchiolitis is an inflammation of the smaller lower airways (bronchioles). Bronchiolitis mainly occurs in children under the age of 2 and is often caused by RS-virus (RSV). More information about the definition of bronchiolitis can be found in the the background and methods document on respiratory surveillance for 2024/2025.
Peak around New Year's
The weekly number of children under 5 years old who visited the GP for bronchiolitis during the 2024/2025 respiratory season showed the same trend as the sources from the RSV-specific surveillance. Around the turn of the year from 2024 to 2025, there was a peak both in the number of young children with bronchiolitis at the general practitioner and in the number of times RS-virus was detected. The timing of this peak was later than in the previous season (2023/2024), but almost the same as in the last five respiratory seasons before the COVID-19 pandemic (2014/2015 through 2018/2019). For more information, see the annual report on respiratory surveillance 2018/2019. The size of the peak in the number of children with bronchiolitis at the GP was similar to that in the previous respiratory season (2023/2024).
Pneumonia in primary care
In the respiratory season 2024/2025, a total of 216 patients per 10,000 inhabitants visited the GP due to pneumonia. This is based on data from Nivel Primary Care Database. This number is lower than in respiratory season 2023/2024, but similar to the 2022/2023 season and the last four respiratory seasons before the COVID-19 pandemic (2015/2016 through 2018/2019). For more information, see the annual report on respiratory surveillance 2018/2019.
From week 45 of 2024, the number of patients with pneumonia increased. This reached a peak in week 6 of 2025, with 9.5 GP visits per 10,000 inhabitants. This peak was lower than in the respiratory season 2023/2024 but occurred at the same timepoint in the season.
The weekly number of patients who visited the GP for pneumonia during the respiratory season 2024/2025 was highest among people aged 65 years and older, followed by children in the 0 to 4 years age group. The number of GP visits in these age groups was at a similar level to that of the 2022/2023 season and the seasons before the COVID-19 pandemic.
CAP - 16 CAP cumulatief
Skip chart Figure 16. Total number of general practitioner visits for pneumonia per 10,000 inhabitants, during the respiratory season (week 40 through week 20) from 2015/2016 through 2024/2025 and outside the respiratory season (week 21 through week 39) from 2015/2016 through 2023/2024. (Source: Nivel Primary Care Database) and go to datatableSevere Acute Respiratory Infections (SARI)
Severe Acute Respiratory Infections (SARI) are respiratory infections requiring hospital admission. Starting this year, the RIVM has weekly data on the number of patients admitted to the Intensive Care Unit (ICU)* due to SARI. These data originate from the National Intensive Care Evaluation (NICE) registry. They share anonymous and aggregated data with the RIVM every week. In May 2025, 15 out of the 70 ICUs provided daily data to the NICE registry, after which the data was delivered weekly to the RIVM. More information about the SARI definition can be found in the background and methods document on respiratory surveillance for 2024/2025.
Most SARI admissions during the influenza epidemic
During the 2024/2025 respiratory season, a total of 858 patients were admitted to the 15 ICUs for which weekly data were available for SARI surveillance in May 2025. There are 70 ICUs in the Netherlands in total. The number of admissions during the 2024/2025 respiratory season was similar to the number of admissions in the previous respiratory season 2023/2024 (910 admissions). The number of weekly ICU admissions peaked in week 5 of 2024, reaching 53 patients. This peak occurred during the influenza season, which started in week 3 of 2025. This peak was similar to that of the previous influenza season, when the highest number of admissions was reached in week 3 of 2023 with 49 admissions. During the increases in SARS-CoV-2 in the summer and autumn of 2024, no clear increase was observed in the weekly number of SARI ICU admissions.
*This information does not apply to pediatric intensive care units (PICU).