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Using participatory, virologic, and wastewater surveillance systems, we estimated when and to what extent reported data of adult COVID-19 cases underestimated COVID-19 incidence in Germany. We also examined how case underestimation evolved over time. Our findings highlight how community-based surveillance systems can complement official notification systems for respiratory disease dynamics.

As part of the national influenza pandemic preparedness, surveillance systems have been established in Germany in addition to the mandatory notifications according to the Protection Against Infection Act. The aim of these systems is the description, analysis, and evaluation of the epidemiology of acute respiratory infections (ARIs), the identification of the circulating viruses, and the trend. Since the beginning of the COVID-19 pandemic, the systems have been expanded to enable monitoring of infections with SARS-CoV‑2.Three systems are presented: GrippeWeb, the primary care sentinel Arbeitsgemeinschaft Influenza with its electronic reporting module SEED ARE , and the ICD-10-based hospital sentinel ICOSARI. With these systems, ARIs can be monitored at the population, outpatient, and inpatient levels. In combination with the monitoring of mortality, these systems provide important information on the frequency of different stages of disease severity in the population. In order to expand the systems to SARS-CoV‑2, only a few adjustments were needed.As the case definitions for ARIs were preserved, historical baselines of the systems can still be used for comparison. All systems are structured in such a way that stable and established reference values are available for calculating weekly proportions and rates.This is an important addition to the mandatory reporting system of infectious diseases in Germany, which depends on the particular testing strategy, the number of tests performed, and on specific case definitions, which are adapted as required.The surveillance systems have proven to be feasible and efficient in the COVID-19 pandemic, even when compared internationally.

Background: Internet-based participatory surveillance systems, such as the German GrippeWeb, monitor the frequency of acute respiratory illnesses on population level. In order to interpret syndromic information better, we devised a microbiological feasibility study (GrippeWeb-Plus) to test whether self-collection of anterior nasal swabs is operationally possible, acceptable for participants and can yield valid data., Methods: We recruited 103 GrippeWeb participants (73 adults and 30 children) and provided them with a kit, instructions and a questionnaire for each sample. In the first half of 2016, participants took an anterior nasal swab and sent it to the Robert Koch Institute whenever an acute respiratory illness occurred. Reporting of illnesses through the GrippeWeb platform continued as usual. We analysed swabs for the presence of human c-myc-DNA and 22 viral and bacterial pathogens. After the study, we sent participants an evaluation questionnaire. We analysed timeliness, completeness, acceptability and validity., Results: One hundred and two participants submitted 225 analysable swabs. Ninety per cent of swabs were taken within 3 days of symptom onset. Eighty-nine per cent of swabs had a corresponding reported illness in the GrippeWeb system. Ninety-nine per cent of adults and 96% of children would be willing to participate in a self-swabbing scheme for a longer period. All swabs contained c-myc-DNA. In 119 swabs, we identified any of 14 viruses but no bacteria. The positivity rate of influenza was similar to that in the German physician sentinel., Conclusion: Self-collection of anterior nasal swabs proofed to be feasible, was well accepted by participants, gave valid results and was an informative adjunct to syndromic data., (© 2019 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd.)

Background: Every year epidemic waves of influenza and other acute respiratory infections (ARIs) cause a highly variable burden of disease in the population. Thus, assessment of the situation and adaptation of prevention strategies have to rely on real time syndromic surveillance., Objective: We have established an ICD-10-based electronic system allowing rapid capture and transmission of information on ARI (SEED ARI ), in Germany. Here we report the evaluation of this new system based on results of the syndromic and virologic surveillance carried out by the working group on influenza in Germany (AGI)., Methods: Consultations and ICD10-codes (J00-J22, J44.0 and B34.9) between week 16 in 2009, and week 15 in 2013, were used for comparison with AGI data. The time course and the correlation of weekly estimates of the incidence of medically attended ARI (MAARI) and ARI/100 consultations were analyzed for the different surveillance systems., Results: The number of participating medical practices in SEED ARI almost doubled from 2009 (n = 65) to 2013 (n = 111). A total of almost 6.8 million consultations and 465,006 diagnosed ARIs were transmitted. The comparison of weekly estimated incidence of MAARI per 100,000 capita derived from SEED ARI and the results of the AGI showed high statistical correlation (Spearman correlation coefficient r s  = 0,924; n = 209; p < 0,001). The proportion of diagnosed influenza (J09-J11) and the weekly positivity rate from virological surveillance during epidemic waves also showed high correlations., Discussion: We conclude that SEED ARI represents a valid system for syndromic influenza surveillance. The case-based ICD-10 approach allows a detailed analysis of the actual situation and also seems suitable for population-based studies.