Parainfluenza Virus Type 3 Co-infection with Other Respiratory Pathogens Among Hospitalized Children with Acute Respiratory Infections in Wuhan, China

Background: Bacterial and viral co-infections are increasingly recognized as the cause of Acute Respiratory Infection (ARI). The role of co-infection in ARI patients with Parainfluenza Virus type 3 (PIV3) infection is unclear. Objectives: This study aimed to determine the prevalence of PIV3 co-infections in hospitalized children and assess the co-infections' role in ARI patients with PIV3 infections. Methods: Between January 2018 and December 2021, children were confirmed to have a PIV3 infection via throat swabs or nasopharyngeal aspirates. Some digital clinical data were analyzed, including demographic, epidemiological, diagnostic, and laboratory data. Results: During the study period from 2018 to 2021, 2,539 patients were hospitalized with ARI caused by PIV3. Of them, 34.0% had co-infection with other pathogens, and 2.4% had co-infection with more than two pathogens. Mycoplasma pneumoniae was the most common co-infecting pathogen (71.3%), followed by other bacteria (13.3%) and viruses (8.2%). A significantly higher proportion of patients with M. pneumoniae co-infection was found in girls (χ2 = 19.233, P < 0.001). Co-infections with M. pneumoniae were observed principally in patients aged 1 – 2 years (χ2 = 202.130, P < 0.001). In contrast, viral (56.3%) and bacterial (66.1%) co-infections occurred mainly in children younger than one year. The diagnosis of PIV3 as a single infection included pneumonia (41.2%), bronchitis (39.9%), upper respiratory tract infections (15.0%), and laryngitis (3.9%), which were distinguished from those with bacterial co-infections (χ2 = 16.424, P = 0.001) and co-infections with more than two pathogens (χ2 = 11.687, P = 0.010). Co-infections of PIV3 with any pathogen were not associated with admissions to intensive care units or ventilator support. However, the mean hospitalization was significantly higher in M. pneumoniae co-infections (t = 2.367, P = 0.018), bacterial co-infections (t = 2.402, P = 0.016), and co-infections with more than two pathogens (t = 2.827, P = 0.006) than in single PIV3 infection. Conclusions: Parainfluenza virus type 3 frequently occurs with other pathogens. The epidemiological and clinical characteristics of co-infections with different pathogens differed. Mycoplasma pneumoniae co-infections, bacterial co-infections, and co-infections with more than two pathogens lengthened the hospitalization. Bacterial co-infections and co-infections with more than two pathogens increased the severity of ARI and worsened the symptoms.