One Sample, Many Insights: The Epidemiological and Public Health Value of Multiplex PCR Respiratory Panels Following the End of the COVID-19 Pandemic

Background: Molecular diagnostics may detect several respiratory pathogens simultaneously with rapid turnaround times. The aim of this study was to determine the frequency and distribution of respiratory pathogens among symptomatic outpatients. Methods: All outpatients presented for testing due to suspected acute respiratory infection between 1 January and 31 December 2024 to the Teaching Institute for Public Health of Split-Dalmatia County, Croatia, and multiplex real-time PCRs for 13 respiratory pathogens were included. Results: Out of 15,437 analyzed panels, 8878 (57.5%) were positive. Single-pathogen infections dominated (82.6%), while co-infections were recorded in 17.4% of panels; therefore, a total of 10,546 individual pathogens were detected, which were mostly viruses (87.0%). The following distribution of pathogens was observed: rhinovirus/enterovirus in 38.9% of positive results, influenza A virus in 14.5%, SARS-CoV-2 in 9.5%, parainfluenza virus in 7.9%, respiratory syncytial virus in 7.3%, Mycoplasma pneumoniae in 4.9%, Bordetella pertussis in 4.6%, human metapneumovirus in 4.2%, adenovirus in 3.4%, Chlamydia pneumoniae in 3.4%, influenza B virus in 1.3%, Bordetella parapertussis in 0.1% and Legionella pneumophila had one positive result. The first trimester of the year had the highest number of positive test panels (47.0%). Conclusions: Our study demonstrates a predominance of viral pathogens across all age groups and seasons, further supporting guideline-based practice and highlighting the importance of confirming bacterial infection before initiating antibiotic therapy. This insight into the post-pandemic circulation of respiratory pathogens may help inform public health strategies, including improved surveillance, anticipation of seasonal outbreaks, and targeted interventions, thereby supporting future pandemic preparedness and mitigation efforts.