Respiratory viruses

Respiratory viruses such as influenza, SARS-CoV-2 and respiratory syncytial virus (RSV) cause colds. Some people develop severe illness or complications that can lead to hospitalisation. The risk can be reduced by having the appropriate vaccinations for the flu or COVID-19 in autumn.

Infections, especially with the flu and RSV, are more common in the winter months. However, surveillance for the relevant pathogens is done throughout the year. Various systems are used to collect data. Background information on the individual collection systems can be found on the FOPH Infectious Diseases Dashboard (IDD).

Key figures on respiratory viruses in Switzerland and Liechtenstein

On the FOPH Infectious Diseases Dashboard you’ll find figures on the current spread of respiratory viruses as well as on the situation regarding viral colds and the resulting burden of disease in Switzerland and the Principality of Liechtenstein. The FOPH Infectious Diseases Dashboard also shows key figures on the specific pathogens influenza and SARS-CoV-2.

Previous reports on seasonal flu and COVID-19

Analysing and monitoring wastewater

Wastewater monitoring: keeping track of the epidemiological situation for respiratory pathogens

People who become infected with respiratory viruses such as SARS-CoV-2, Influenza A, Influenza B or RSV excrete fragments of the virus’s genetic material (such as RNA) in their stool. Such fragments thus get into the wastewater system and can be detected there. Since February 2021 the Swiss Federal Institute of Aquatic Science and Technology (Eawag) has been collecting daily samples of wastewater from six Swiss water treatment plants and analysing these for the presence of SARS-CoV-2. These analyses can help determine whether and (if so) to what extent people are infected with SARS-CoV-2 within the catchment area of the treatment plant concerned.

Eawag has also been conducting research projects on detecting SARS-CoV-2 in wastewater since summer 2020. As part of this project programme, the associated water analyses have been gradually expanded to include further pathogens. The projects’ findings have also been used to establish a nationwide SARS-CoV-2 monitoring system.

Monitoring wastewater is an efficient way to keep track of the present viral load and of the virus variants currently circulating in the population. It provides reliable data rapidly, anonymously and over an extensive area, which is particularly useful when fewer and fewer COVID-19 tests are being conducted.

With the transition to the post-pandemic SARS-CoV-2 situation, the extent of Switzerland’s nationwide wastewater monitoring has been gradually scaled back. In 2022, samples were taken three to six times a week from some 100 water treatment plants (covering around 70% of the population) and analysed by designated cantonal and private laboratories. In January 2023, in view of the COVID-19 epidemiological situation, the range of water treatment plants sampled was reduced to around 50 (covering 44% of the population). And in July 2023, all the analyses under this national wastewater monitoring were taken over by Eawag, and the number of treatment plants sampled was further reduced to 14 (covering 27% of the population). To provide integrated monitoring of respiratory viruses, this national wastewater monitoring programme was also expanded to include influenza and RSV.

The institutionalisation of wastewater monitoring in Switzerland has established a sustainable and scalable system for monitoring respiratory pathogens. The selection of the water treatment plants sampled pays due regard to both their geographical distribution and the structure of their catchment areas, i.e. whether these are largely urban or rural by nature. The costs of these analyses are met by the federal government.

The data collected to track the epidemiological situation are evaluated on an ongoing basis. The data on SARS-CoV-2 can be found on the FOPH Infectious Diseases Dashboard (IDD). And further information on the methodology and results will be found on the Eawag website and on the ETH’s wastewater monitoring webpage.

Wastewater-based SARS-CoV-2 monitoring in various countries

In the document below you will find an overview of how a selection of countries are monitoring the spread and distribution of SARS-CoV-2 by sampling and analysing their wastewater.

Monitoring of COVID-19 and flu in Swiss hospitals

During the pandemic, the hospital-based sentinel system proved to be an important tool for monitoring severe disease progression in COVID-19 and flu. The surveillance system was launched in 2018 as part of flu surveillance and expanded to include COVID-19 in 2020.

The aim of such monitoring is to obtain detailed clinical and epidemiological information on the burden of disease, its clinical course (such as ICU treatment) and risk factors. CH-SUR is being jointly coordinated by the FOPH, the Institute of Global Health of the University of Geneva and the Infection Control Program of the Geneva University Hospitals (HUG). The project is financed by the FOPH.

The key results and findings from the hospital-based sentinel system are published weekly in a joint report in English, French, German and Italian. Reporting is seasonal and commences in mid-October. You can find the latest report, along with previously published reports here. Background information on the survey system can be found on the FOPH Infectious Deseases Dashboard (IDD) or on the website of the University of Geneva (flu and COVID-19).

Latest edition

Previous reports from hospital-based monitoring of the flu and COVID-19


Further information

Seasonal flu (influenza)

The flu is a common infectious disease in wintertime. The risk of getting the flu and its complications can be reduced by vaccination. It is recommended for risk groups and their contact persons.


Information on COVID-19, the symptoms and the range of illness severity as well as the origin of the coronavirus.

Last modification 16.05.2024

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