Comparative analysis of acute intestinal infections of polymicrobial etiology identified in children's and adult infectious diseases hospitals

Acute intestinal infections (AII) are among the most common infections and are caused by a wide range of pathogens. In recent years, polymicrobial AIIs have been increasingly diagnosed; however, their epidemiological characteristics remain poorly understood. Objective. To identify the epidemiological characteristics of polymicrobial AIIs diagnosed in pediatric and adult infectious disease hospitals. Materials and methods. A retrospective analysis of AII cases from January 1, 2023, to December 31, 2025, identified in patients at pediatric and adult infectious disease hospitals in St. Petersburg. Results. The proportion of polymicrobial AIIs (including only associations of bacterial and/or viral intestinal pathogens) among cases with an established etiology was 8.58 %, 6.32 %, and 12.69 % (p < 0.01) in the adult and pediatric infectious disease hospitals, respectively. Viral and bacterial acute intestinal infections were the most frequently detected (67.65 %, 57.45 %, and 80.21 %, respectively, p<0.05). Among the associations, the most frequently recorded were Norovirus with Rotavirus (29.18 %) and Norovirus with Campylobacter sp. (17.5 %) in the adult infectious diseases hospital, Rotavirus with Campylobacter sp. (25.9 %), and Rotavirus with Salmonella sp. (20.1 %) in the pediatric infectious diseases hospital. The highest number of adult hospitalizations with polymicrobial acute intestinal infections is observed in January and August, while the highest number of children hospitalized with polymicrobial acute intestinal infections is observed in August-December. Conclusion. Polymicrobial acute intestinal infections are detected in children twice as often as in adults. The epidemiological features of the incidence of polymicrobial acute intestinal infections include the predominance of Norovirus in associations in adults and Rotavirus in associations in children. Significant differences were revealed in the intra-annual dynamics of acute intestinal infections of viral-viral, viral-bacterial and bacterial-bacterial etiology both among themselves and among children and adults.