Sentinel surveillance of acute respiratory infections and distribution of SARS-CoV-2, influenza A and B, and respiratory syncytial virus in the post-COVID-19 period

Mioljub Ristić; Aleksandra Patić; Ana Miljković; Nataša Nikolić; Galina Gavanski; Gordana Kovačević; Vladimir Petrović

doi:10.2298/VSP250402052R

Mioljub Ristić Institute of Public Health of Vojvodina, Novi Sad, Serbia; University of Novi Sad, Faculty of Medicine, †Department of Epidemiology, Novi Sad, Serbia
Aleksandra Patić Institute of Public Health of Vojvodina, Novi Sad, Serbia; University of Novi Sad, Faculty of Medicine, Department of Microbiology with Parasitology and Immunology, Novi Sad, Serbia
Ana Miljković Department of General Medicine and Geriatrics, Novi Sad, Serbia; ||Health Center Novi Sad, Novi Sad, Serbia
Nataša Nikolić Institute of Public Health of Vojvodina, Novi Sad, Serbia; University of Novi Sad, Faculty of Medicine, Department of Microbiology with Parasitology and Immunology, Novi Sad, Serbia
Galina Gavanski Health Center Novi Sad, Novi Sad, Serbia
Gordana Kovačević Institute of Public Health of Vojvodina, Novi Sad, Serbia
Vladimir Petrović Institute of Public Health of Vojvodina, Novi Sad, Serbia; University of Novi Sad, Faculty of Medicine, Department of Epidemiology, Novi Sad, Serbia

DOI: https://doi.org/10.2298/VSP250402052R

Keywords: epidemiology;, influenza a virus;, influenza b virus;, respiratory syncytial viruses;, respiratory tract infections;, sars-cov-2.

Abstract

Background/Aim. Acute respiratory infections (ARIs) remain a major global health concern. The aim of this study was to analyze the epidemiological and clinical characteristics of ARIs and detect the distribution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A, influenza B, and respiratory syncytial virus (RSV) among outpatients during the 2023/24 and 2024/25 seasons. Methods. A prospective study was conducted through sentinel surveillance, enrolling only patients with ARI symptoms/signs. Identification of one of the four viruses was performed using the CerTest SARS-CoV-2 + Flu A + Flu B + RSV rapid combined test. Results. In the 2023/24 season, 26.57% of samples tested positive for at least one virus, while in the 2024/25 season, a decrease in positivity for the tested viruses was observed, dropping to 14.24%. Influenza A dominated during the 2023/24 season, while the incidence of influenza B increased in early 2025, peaking in late February. SARS-CoV-2 showed moderate fluctuations throughout the study period, with a pronounced peak in September 2024, while RSV remained low during both seasons. The age distribution of patients varied: in the 2023/24 season, RSV and influenza B were most frequently recorded in young children aged 0–4 years, influenza A in children aged 0–4 and 5–14 years, while SARS-CoV-2 was most prevalent among adults aged 30–64 years. In the 2024/25 season, RSV and influenza A were most commonly diagnosed in children aged 0–4 years, influenza B in children aged 5–14 years, and SARS-CoV-2 in individuals over 30 years old. Elevated body temperature was the most common symptom regardless of the type of confirmed viral infection but was significantly less present in SARS-CoV-2 infections compared to other viruses. Conclusion. The results of this study indicate a shift in the dominance of viral causative agents between the observed seasons, with influenza A prevailing in 2023/24, while an increase in the incidence of influenza B virus was observed in 2024/25. SARS-CoV-2 circulated continuously but at a low level, while the impact of RSV was minimal in both seasons.

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