Absences, Symptoms and Respiratory Viruses in a Swiss School: Longitudinal Study With Serial Saliva Sampling.

Background Viral respiratory infections contribute to sick days in school children. We monitored respiratory infections, absences, and symptoms in a Swiss school.Methods Serial saliva sampling (three per week) and daily recording of absences and symptoms over 6 weeks during the winter of 2023/24 in four Swiss school classes (age 14-15).Results We analyzed 1047 samples of 67/84 (80%) participants, identifying 87 infection episodes across eight viruses: 28 (32%) human rhinovirus, 18 (21%) influenza A/B, 11 (13%) respiratory syncytial virus, 14 (16%) human coronaviruses, 6 (7%) parainfluenza virus, and 5 (6%) influenza B; SARS-CoV-2 was not detected. Spatiotemporal trends revealed seasonal epidemic trends and evidence of transmission within classes. Viral loads (interquartile range 29.5-36.9 Ct) and duration of detection (modeled range 3.2-5.3 days) were similar for all viruses. School absences were more likely temporally associated with influenza B infections than with other respiratory viral infections (> 99% vs. 38%, p = 0.005), and the absences tended to be longer (average 4.2 vs. 2.2 days). Symptoms varied depending on the pathogen detected, with absences temporally associated with human rhinovirus and parainfluenza virus infections commonly involving runny nose and sore throat, while absences associated with influenza infections often involved fever.Conclusions Class-specific distribution patterns suggest a major contribution of within-class to overall respiratory virus transmission. Respiratory viruses showed certain distinct profiles in relation to school absences and symptoms. This highlights the importance of infection control measures, including vaccination, and virus-specific monitoring to better understand transmission dynamics in schools.