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Annual report Surveillance of acute respiratory infections in the Netherlands: winter 2022/2023. SARS-CoV-2, influenza virus, RSV and other respiratory viruses.

Reukers, D.F.M., Asten, L. van, Hooiveld, M., Jongenotter, F., Lange, M.M.A. de, Teirlinck, A.C., Veldhuijzen, I.K., Meijer, A., Gageldonk-Lafeber, A.B. van. Annual report Surveillance of acute respiratory infections in the Netherlands: winter 2022/2023. SARS-CoV-2, influenza virus, RSV and other respiratory viruses. Bilthoven: National Institute for Public Health and the Environment (RIVM), 2023. 104 p. p.
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Synopsis

Surveillance of acute respiratory infections in the Netherlands: winter 2022/2023

Each year, RIVM presents an overview of how many persons in the Netherlands got the flu and other respiratory infections. Since 2020, this report has also included an overview of how many people contracted the coronavirus SARS-CoV-2. Many respiratory infections showed reduced circulation during the first COVID-19 epidemic years. However, during the 2022/2023 winter season, many pathogens showed pre-epidemic numbers of detections again or even exceeded the numbers in previous seasons.

Coronavirus
Between May 2022 and May 2023, there were 4 waves in the SARS-CoV-2 epidemic in the Netherlands, all caused by the Omicron variant. This variant caused less severe illness than previous variants, resulting in fewer hospital admissions. In this period, 28,633 persons with a positive SARS-CoV-2 test were admitted to the hospital of which 1,812 persons were admitted to intensive care. From May 2022 to May 2023, 5,349 persons died as a result of COVID-19.

Flu epidemic
The flu epidemic in the winter of 2022/2023 started in week 50 and lasted 14 weeks. About 169,000 people went to their GP with flu-like illness. This was higher than previous season, but still lower than the seasons before the COVID-19 epidemic. An estimated 837,000 persons have had the flu between October 2022 and May 2023. Most people became ill from the type A(H1N1)pdm09 and B (Victoria lineage) influenza virus, but influenza virus type A(H3N2) was also frequently detected. People who got the flu shot were 52 percent less likely to get the flu.
That is comparable to the seasons before the COVID-19 epidemic.

RSV
At the end of the summer of 2022, the number of RSV detections started to decrease, after more than a year of increased circulation in the Netherlands. The number of detections and the number of hospital admissions of children below 2 years of age started to increase again in the autumn and reached a peak in the last weeks of 2022. The total number of RSV detections in the winter of 2022/2023 was much higher than previous seasons. It is not clear whether there were actually more patients or whether infections were reported more often. Hospitals
often combine the test for SARS-CoV-2 with RSV, so RSV infections could also be observed more often.