Viral etiology of acute respiratory tract infection among children under 5 years of age in Kunming City, China: a matched case–case–control study

Nucleic acid-based molecular techniques in current laboratory practice allow the identification of a broad range of respiratory viruses. However, due to asymptomatic carriage, the detection of viruses in the respiratory tract does not necessarily indicate disease. The study aimed to investigate infections of different viruses that colonize the airways, the viral combinations in coinfection, and the viral association with the occurrence of either upper respiratory tract infection (AURTI) or lower respiratory tract infection (ALRTI) in children.A matched case-case-control study included ALRTI cases, AURTI cases, and healthy controls was conducted at Kunming Children's Hospital. Oropharyngeal swabs from the three groups were collected for eight viral pathogens detection by multiplex RT-PCR. The association of each pathogen with disease status was determined by comparing the results between cases and controls. From 1 March 2021 through 28 February 2022, 278 participants in each group were investigated. Viral infection was detected in 54.0%, 37.1%, and 12.2% of the ALRTI cases, AURTI cases, and healthy controls, respectively. Human respiratory syncytial virus (RSV), adenovirus (ADV), and parainfluenza virus-3 (PIV-3) were the most frequently documented viruses. RSV/ADV was the most frequent combination detected in coinfection. When compared to healthy controls, RSV and PIV-3 were independently associated with both ALRTI and AURTI.RSV and PIV-3 were causes of both ALRTI and AURTI cases. These results provide initial evidence of the potential of microbiota-based diagnostics for the differential diagnosis of severe acute respiratory infections using oropharyngeal swab samples.