Challenges in Infection Epidemiology: On the Underreporting of Norovirus Gastroenteritis Cases in Germany

Abstract

It is commonly accepted that the number of officially reported incidences of norovirus (NoV) according to the German Protection against Infection Act (Infektionsschutzgesetz) does not reflect the ‘true’ incidence of NoV in Germany. This study aims to reveal the reasons for the underreporting of NoV cases by comparing secondary data. Methods: NoV incidence (cases per 100,000 reference persons) in the age group 18–65 was derived from register data of four different sources in the German public health system (2011–2015): Statutory health insurance in the federal state of Lower Saxony (AOK; in- and outpatient cases), the Research Institute of Ambulatory Health Care in Germany (ZI; outpatient cases), the German Federal Statistical Office (inpatient cases; DESTATIS), and the Robert Koch Institute (RKI SurvStat; health reporting data). Results: the incidence derived from the AOK in Lower Saxony varied between 49 and 66 NoV cases per 100,000 persons and was thus lower than at the federal level. Incidences of all inpatient and outpatient data were lower than the incidence according to the RKI in the last 2–3 years of the observation period. Conclusions: the disagreement between NoV incidences calculated from secondary inpatient and outpatient data and the respective numbers published by the RKI can be regarded as an indication that not all NoV cases were reported to public health authorities. This might be due to missed cases during the notification procedure or misclassification of gastroenteritis cases by general practitioners. Considering the limitations associated with analyzing secondary data, the appropriateness of these assumptions should be verified in future studies.

Significance of norovirus in occupational health: a review of published norovirus outbreaks in Central and Northern Europe

“…This is also supported by an earlier study of us. Based on register data from Lower Saxony, we showed that the incidence of NoV among HCWs was significantly higher relative to the incidence of NoV in the total population (Hofmann et al 2018).…”

Amplicon-Based High-Throughput Sequencing Method for Genotypic Characterization of Norovirus in Oysters

“…However, these studies focused on application rather than optimization and did not confirm HTS results with the gold standard Sanger methods. Due to the high degree of underreporting of norovirus cases, particularly nonnosocomial cases in healthy populations ( 17 , 18 ), samples tend to come from foodborne outbreaks requiring source attribution or chronic nosocomial cases. This skews our understanding of norovirus genotypes circulating in local populations and will limit effective vaccine production and management of clinical cases ( 19 ).…”

Development of an amplicon-based high throughput sequencing method for genotypic characterisation of norovirus in oysters

“…However, these studies focused on application rather than optimisation and did not confirm HTS results with the gold standard Sanger methods. Due to the high degree of underreporting of norovirus cases, particularly non-nosocomial cases in healthy populations (18, 19), samples tend to come from food-borne outbreaks requiring source attribution or chronic nosocomial cases. This skews our understanding of norovirus genotypes circulating in local populations and will limit effective vaccine production in the future and management of clinical cases (20).…”