This retrospective observational study aims to evaluate changes in the prevalence and distribution of respiratory pathogens detected by multiplex respiratory polymerase chain reaction (PCR) testing during and after the SARS-CoV-2 pandemic. The study includes 537 patients presenting with respiratory infection symptoms at a tertiary care center. Patients were divided into pandemic-period and post-pandemic-period groups, and respiratory pathogen profiles were compared between the groups.

The study investigates the epidemiological impact of COVID-19-related public health measures on respiratory pathogen circulation patterns, including bacterial and viral respiratory infections. The findings may contribute to improved respiratory infection surveillance, diagnostic strategies, and post-pandemic public health preparedness.

The COVID-19 pandemic significantly altered the epidemiology of respiratory infections worldwide. Non-pharmaceutical interventions (NPIs), including mask use, social distancing, travel restrictions, enhanced hygiene measures, and lockdown policies, were implemented primarily to reduce SARS-CoV-2 transmission. However, these interventions also affected the circulation patterns of other respiratory pathogens.

Several studies have demonstrated substantial reductions in influenza, respiratory syncytial virus (RSV), and other respiratory viral infections during periods of strict public health measures. Following the relaxation of these interventions, many regions experienced re-emergence and altered seasonal patterns of respiratory pathogens. Continuous surveillance of respiratory infections has therefore become increasingly important for both clinical management and public health preparedness.

This retrospective observational cohort study aims to evaluate changes in respiratory pathogen prevalence during and after the SARS-CoV-2 pandemic using multiplex respiratory PCR testing data obtained from patients presenting with respiratory infection symptoms at a tertiary care center. A total of 537 patients were included and categorized into pandemic-period and post-pandemic-period groups.

Demographic characteristics and multiplex PCR results were analyzed and compared between the groups. Respiratory pathogens evaluated in the study included bacterial and viral agents such as Streptococcus pneumoniae, Haemophilus influenzae, Influenza A/B, SARS-CoV-2, RSV, Rhinovirus, Bocavirus, Parainfluenza virus, Coronavirus, and Metapneumovirus.

The study aims to contribute to understanding the long-term epidemiological effects of the COVID-19 pandemic and associated public health measures on respiratory pathogen distribution. In addition, the findings may support future infection surveillance strategies, diagnostic approaches, and healthcare preparedness in post-pandemic periods.

Inclusion Criteria:

• Adults and/or pediatric patients presenting with respiratory infection symptoms
• Patients who underwent multiplex respiratory PCR testing
• Patients with complete demographic and laboratory records
• Patients included during the defined pandemic or post-pandemic study periods

Exclusion Criteria:

• Incomplete laboratory or demographic data
• Duplicate test records from the same infection episode
• Invalid or inconclusive PCR results
• Patients without respiratory infection symptoms

The study population consisted of patients presenting with respiratory infection symptoms who underwent multiplex respiratory polymerase chain reaction (PCR) testing at a tertiary care center during the pandemic and post-pandemic periods. Patients with complete demographic and laboratory data were included in the analysis.

Individual participant data (IPD) will not be shared because this retrospective study contains hospital-based patient data, and sharing such data may compromise patient confidentiality and institutional data protection policies.