Co-occurrence of viral respiratory pathogens: prevalence, seasonal distribution, and symptomatology in outpatients in Bavaria, Germany, from April 2025 - March 2026.

Authors

Aline I Schöllkopf, Jennifer Flechsler, Rebecca Gerstner, Johannes Lutmayr, Alexander Nikola, Julia Papst, Sandra Schmidt, Veronika Zacherl, Caroline Herr, Ute Eberle, Andreas Sing, Nikolaus Ackermann

Published in

Infection. Oct 12, 2026. Epub Oct 12, 2026.

Abstract

The Bavarian Influenza Sentinel (BIS + C) monitors the circulation of respiratory viruses in outpatients in Bavaria, Germany. After the Covid-19 pandemic, the molecular surveillance program was expanded for improved insight into the rate of viral infections. Only limited information on viral co-infections is yet available, so this study provides an insight into their co-occurrence, seasonal distribution, and symptomatic outcome.
From calendar week 15/2025 to 14/2026, general practitioners and pediatricians collected swab samples from outpatients with acute respiratory diseases, that were tested for twelve viral pathogens using qPCR multiplex systems.
At least one virus was found in 58.8% of the outpatients (n = 7,416/12,614) including 4.1% (n = 520) multiple viral detection, primarily in patients younger than 5 years and more frequent in males. The frequency of multiple virus detection ranges from 6.7% in influenza A (n = 118/1,761) to 43.3% in adenoviruses (n = 154/356) positive tested samples. The most common pathogens in multiple detections were entero-/rhinoviruses involved in 11.9% (n = 292/2,459). Differences in the reported symptoms between single- and co-infections have been found, including less muscle/joint pain in influenza A co-infections. The detected Ct values in co-infections compared to mono-infections were lower for SARS-CoV-2, adenoviruses, entero-/rhinoviruses, and coronaviruses.
The frequency of multi-infections follows the seasonality of the corresponding viruses. Especially children under 5 years of age are affected by co-infections. Among the studied viruses, influenza A showed the lowest relative rate of co-detection, in line with its pronounced seasonality - a pattern that warrants further investigation.

PMID:
42862470
Bibliographic data and abstract were imported from PubMed on 13 Oct 2026.

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