Objective To investigate and analyze the epidemiological characteristics and cause of an acute respiratory infection outbreak in L Middle and Primary School of Sichuan and provide a reference for the investigation and response of similar emergencies in the future.

Methods Epidemiological investigation was conducted for possible cases. Throat swabs were collected from the teachers and students for nucleic acid detections of severe acute respiratory syndrome coronavirus (SARS-CoV-2) and influenza viruses, and 42 kinds of pathogens were detected by using the respiratory pathogen microfluidic chip real-time fluorescent quantitative PCR.

Results A total of 62 possible cases and 7 confirmed cases were found. The main clinical symptoms and signs were cough (80.65%) and pharyngeal congestion (75.81%). The nucleic acid test results of 441 throat swabs were negative for SARS-CoV-2 and influenza A/B viruses. The results of 42 pathogen tests on throat swabs from 7 hospitalized cases showed that 7 cases were Haemophilus influenzae positive and 5 cases were rhinovirus positive.

Conclusion SARS-CoV-2 and influenza virus infections were excluded in this respiratory infection outbreak, the outbreak might be caused by the infections of H. influenzae and rhinovirus after sudden change of weather. It is necessary for schools to further standardize the inspections in the morning, afternoon and evening to detect and report epidemic as early as possible. When epidemic occur in schools or other public places, it is important to conduct early intervention and timely control. Meanwhile, health education should be strengthened to suggest students to wear warm clothes in case of weather change.