How is the activity of acute respiratory infections monitored in Germany?

In order to estimate the activity of acute respiratory infections (ARI), it is required to evaluate several data sources together. The current data are published in weekly reports on ARI by RKI. Some data sources are updated daily (see diagrams). Here, you find an explanation of the difference sources and their meaning.

Notifications according to the Protection against Infection Act: Detections of influenza viruses, SARS-CoV-2 and (since the end of July 2023) RSV are to be notified according to the Protection against Infection Act (IfSG), i.e. laboratories must notify a detection to the respective local health authority. The local health authority identifies further information about the patient who has contracted one of these reportable respiratory infections and then transmits the data to the respective state health authority. From there, the data are sent to the Robert Koch Institute. Not everyone with symptoms of an ARI consults a doctor, and not every ARI patient is tested there. Usually, doctors only take samples from the respiratory tract of some ARI patients and have them tested in a laboratory, although it can be assumed that the amount of testing has increased since the COVID-19 pandemic. For estimating the burden of disease, the data from the reporting system are therefore only suitable to a limited extent because they are very dependent on the frequency of testing and the recommendations for diagnostics for the respective pathogen. The information in the notifiable data according to the Protection against Infection Act is essential for the initiation of infection protection measures at a local level and contains important individual case information, for example on the disease course and vaccination status for further evaluation at the national level. Additionally, the local health authorities are informed via the reports about influenza or COVID-19 outbreaks with several infected persons, for example in old people's homes or in hospitals, and can then support the containment of the outbreak.

Burden of disease/ARI activity: In order to determine the burden of disease at the population level, several hundred general practitioners' and paediatricians' practices (the so-called Working Group Influenza) report the number of patients with acute respiratory diseases to the Robert Koch Institute every week and, as a reference value, the number of all patients who visited their office in the respective week. This enables the determination of the burden of disease caused by ARI (ARI activity).

ARI consultation incidence: The best measure of ARI activity in the outpatient sector is the ARI consultation incidence, i.e. the number of doctor visits due to an ARI per 100,000 inhabitants in the respective age group per week, extrapolated to the entire population on the basis of the reports from the sentinel practices. The sentinel doctors also report the number of hospital admissions and incapacities for work (or need for care) due to an ARI diagnosis.

Online portal GrippeWeb/ARI incidence: Since 2011, the RKI has been asking people in Germany directly via an online portal about acute respiratory illnesses, including flu-like symptoms with fever (GrippeWeb, https://grippeweb.bund.de). The more participants register and answer the weekly question about the occurrence of an acute respiratory illness, the more reliably the seasonal course of respiratory illnesses in general and flu-like illnesses in particular can be tracked. In addition, the data help to estimate the proportion of ill people that consult a doctor. The data are published weekly (in German: www.rki.de/grippeweb and in the weekly ARI report). The ARI incidence of GrippeWeb measures ARI activity even more directly than the ARI consultation incidence, because it is independent of consultation behaviour in the different age groups.

Virological surveillance: The National Reference Centre for Influenza Viruses at the Robert Koch Institute is in charge of virological surveillance within the framework of the Working Group Influenza. About 150 sentinel practices send mainly nasal swabs from patients with typical respiratory symptoms to the Reference Centre. The National Reference Centre analyses the samples by PCR for a broad range of the most common viral respiratory pathogens. The proportions of various respiratory pathogens (including influenza viruses, SARS-CoV-2, RSV, rhinoviruses and human seasonal coronaviruses) is determined in the samples and also published amongst others in the weekly ARI reports. The genetic material of viruses is also examined – for example to monitor how these viruses change genetically and how well vaccines match the circulating viruses.

Hospital surveillance ICOSARI: Since 2015, the RKI has also evaluated information from around 70 sentinel hospitals for the assessment of the flu epidemic and other severe acute respiratory diseases (since 2020 also SARS-CoV-2) and publishes the results in the weekly ARI reports. For this, diagnoses are being analysed of patients with severe acute respiratory infections (SARI) in general and diagnoses of influenza, COVID-19, and RSV respiratory infections in particular. The data from the sentinel hospitals represent the situation and current development of SARI nationwide very well. The surveillance results are transmitted weekly to the ECDC and the WHO.

Wastewater surveillance: Infectious agents enter wastewater via faeces, among other sources, and can be detected there. The systematic monitoring of wastewater for infectious agents with the aim of deciding on population-based measures is called wastewater-based surveillance. Together with the German Environment Agency, the RKI is carrying out the AMELAG project (wastewater monitoring for epidemiological situation assessment), which, in addition to monitoring the SARS-CoV-2 virus load in wastewater, also aims at the expansion to other pathogens or disease indicators. The main results are published in the weekly ARI report as well as in specific wastewater surveillance reports (in German).

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