Hendrik Wilking

After the introduction of the dengue vaccination in spring 2023, 48 cases of dengue infection with a dengue vaccination history were registered between September 2023 and December 2024 among 2079 German travellers with dengue infection returning from abroad.

Foodborne infections represent a significant public health concern, particularly when outbreaks affect many individuals over prolonged time. Systematic collection of pathogen isolates from infected patients, whole genome sequencing and phylogenetic analyses allow recognition and termination of outbreaks after source identification and risk profiling of abundant lineages. We here present a multi-dimensional analysis of >1,800 genome sequences from clinical L. monocytogenes isolates collected in Germany between 2018-2021. These isolates covered 62% of all notified cases and belonged to 188 infection clusters. 42% of these clusters were active for >12 months, 60% generated cases cross-regionally, including 11 multinational clusters. 37% of the clusters were caused by sequence type (ST) ST6, ST8 and ST1 clones and for selected clusters, we provide further epidemiological and genetic information. Frequencies of materno-fetal and brain infections allowed risk profiling of the most abundant STs, differentiating ST1 as hyper- and ST8, ST14, ST29 as well as ST155 as hypovirulent from ST6 with average virulence potential. Hepatocyte infection experiments confirmed these virulence differences. Inactivating mutations were found in several virulence and house-keeping genes, particularly in hypovirulent STs. Our work supports prioritization of clusters for epidemiological investigations and reinforces the need to analyse the mechanisms underlying hyper- and hypovirulence.

Dengue virus (DENV) infections after exposure in Egypt increased in Germany in 2023, with 36 cases vs zero to eight in 2017 to 2022. Over 90% of the patients had stayed on the Red Sea Coast (mostly Hurghada), almost 50% in private residences. Case numbers increased more strongly than traveller numbers. Mosquito control is more difficult in towns than hotel grounds, increasing the risk of infection at private residences. Physicians should consider dengue for unexplained fever after return from Egypt.

During the COVID-19 pandemic in Germany, a variety of societal activities were restricted to minimize direct personal interactions and, consequently, reduce SARS-CoV-2 transmission. The aim of the CoViRiS study was to investigate whether certain behaviours and societal factors were associated with the risk of sporadic symptomatic SARS-CoV-2 infections. Adult COVID-19 cases and frequency-matched population controls were interviewed by telephone regarding activities that involved contact with other people during the 10 days before illness onset (cases) or before the interview (controls). Associations between activities and symptomatic SARS-CoV-2 infection were analysed using logistic regression models adjusted for potential confounding variables. Data of 859 cases and 1 971 controls were available for analysis. The risk of symptomatic SARS-CoV-2 infection was lower for individuals who worked from home (adjusted odds ratio (aOR) 0.5; 95% confidence interval (CI) 0.3–0.6). Working in a health care setting was associated with a higher risk (aOR: 1.5; 95% CI: 1.1–2.1) as were private indoor contacts, personal contacts that involved shaking hands or hugging, and overnight travelling within Germany. Our results are in line with some of the public health recommendations aimed at reducing interpersonal contacts during the COVID-19 pandemic.

In August and September 2023, an unusually high number of cryptosporidiosis cases identified by routine German surveillance had travelled to Croatia (n = 23). Nine cases had stayed in the same camping resort and seven further cases had stayed at other camping sites within 15 km. Based on our standardised questionnaires, the most likely source of infection was swimming pools (93%). Further environmental investigations on site might reveal potential common sources of contamination that could be targeted by control measures.

2. Structured Background: Gastrointestinal infections in Germany account for 24.5 million outpatient visits annually. Surveillance of gastrointestinal infections in emergency departments strengthens timely outbreak detection and disease trend monitoring. Aim: We developed a syndrome definition for automated syndromic surveillance of gastrointestinal infections in emergency departments, and validated it against statutory laboratory-based surveillance. Methods: To develop a syndrome definition, we selected presenting complaints (Canadian Emergency Department Information System) and diagnoses (ICD-10). We validated the definition through time series and cross-correlation analysis, comparing trends between syndromic and laboratory-based surveillance. We analysed German emergency department registry (AKTIN) data and included emergency departments that continuously transferred (01/2019-06/2023) data. As reference we combined statutory norovirus-gastroenteritis, rotavirus-gastroenteritis, campylobacteriosis and salmonellosis notifications. Results: Our syndrome definition combined presenting complaints (diarrhoea, vomiting and nausea) and diagnoses (Intestinal infectious diseases). Accordingly, in 7 emergency departments with n = 864,353 visits, 2.1% ( n = 18,158) were gastrointestinal infection cases. Of those, 57% ( n = 10,424) were female, with 23% 0–19 years ( n = 4,108) and 23% 20–29 years ( n = 4,116) old. We visually observed similar gastrointestinal infection trends in both surveillance systems. The cross-correlation was 0.73 (95%-confidence interval 0.61–0.85; p <0.001) at lag −1, indicating a 1-week relative reporting delay of laboratory-based surveillance. Conclusion: The coherent trends and significant cross-correlation validated our syndrome definition, which adequately captures gastrointestinal infection cases in emergency departments. Our novel automated surveillance complements laboratory-based surveillance, while offering advantages regarding timeliness and reduced workload. Therefore, it will be implemented in national routine surveillance.

Zusammenfassung: Bakterielle zoonotische Erreger sind häufig Auslöser von Erkrankungen mit teilweise schweren Verläufen. Sie sind wechselseitig zwischen Tieren (sowohl Wild- als auch Haustieren) und Menschen übertragbar. Die Transmissionswege sind sehr variabel, so kann die Übertragung u. a. durch orale Aufnahme über Lebensmittel, respiratorische Aufnahme über Tröpfchen und Aerosole sowie über Vektoren wie Zeckenstiche oder Nagerkontakte stattfinden. In diesem Zusammenhang sind auch das Auftreten und die Verbreitung von antibiotikaresistenten bakteriellen Erregern von zunehmender Bedeutung für den öffentlichen Gesundheitsschutz.Die Ausbreitung zoonotischer Erreger wird aktuell durch zahlreiche Faktoren verstärkt. Dazu gehören die Zunahme des internationalen Warenverkehrs, die Einengung der Lebensräume von Tieren und der dadurch zunehmend engere Kontakt zwischen Menschen und Wildtieren. Aber auch eine veränderte Tierhaltung in der Landwirtschaft und Klimaveränderungen können zur Ausbreitung beitragen. Der öffentliche Gesundheitsschutz und die Erforschung von Zoonosen sind deshalb von besonderer krankheitspräventiver, aber auch gesellschaftlicher, politischer und wirtschaftlicher Bedeutung.Ziel dieses Übersichtsartikels ist es, anhand von Beispielen die Spannbreite von Infektionskrankheiten darzustellen, die durch bakterielle zoonotische Erreger ausgelöst werden. Die unterschiedlichen Transmissionswege, epidemischen Potenziale und epidemiologischen Maßzahlen der beispielhaft gewählten Krankheiten sind Herausforderungen für den öffentlichen Gesundheitsdienst, den Tiergesundheitsdienst und die Lebensmittelüberwachung, deren Aufgabe es ist, die Bevölkerung vor diesen Infektionskrankheiten zu schützen.

SARS-CoV-2 serosurveillance is important to adapt infection control measures and estimate the degree of underreporting. Blood donor samples can be used as a proxy for the healthy adult population. In a repeated cross-sectional study from April 2020 to April 2021, September 2021, and April/May 2022, 13 blood establishments collected 134,510 anonymised specimens from blood donors in 28 study regions across Germany. These were tested for antibodies against the SARS-CoV-2 spike protein and nucleocapsid, including neutralising capacity. Seroprevalence was adjusted for test performance and sampling and weighted for demographic differences between the sample and the general population. Seroprevalence estimates were compared to notified COVID-19 cases. The overall adjusted SARS-CoV-2 seroprevalence remained below 2% until December 2020 and increased to 18.1% in April 2021, 89.4% in September 2021, and to 100% in April/May 2022. Neutralising capacity was found in 74% of all positive specimens until April 2021 and in 98% in April/May 2022. Our serosurveillance allowed for repeated estimations of underreporting from the early stage of the pandemic onwards. Underreporting ranged between factors 5.1 and 1.1 in the first two waves of the pandemic and remained well below 2 afterwards, indicating an adequate test strategy and notification system in Germany.