Epidemiological characteristics of human parainfluenza virus infection in acute respiratory infection cases in Henan, 2024–2025

Objective To analyze the incidence status and epidemiological characteristics of human parainfluenza virus (HPIV) infection in acute respiratory infection (ARI) cases in Henan province from 2024 to 2025.

Methods Multiplex quantitative real-time polymerase chain reaction was conducted to detect HPIV and 14 other respiratory pathogens in respiratory samples collected from 19 sentinel surveillance hospitals for acute respiratory infectious diseases and 28 centers for disease control and prevention in Henan. Statistical analyses were conducted for HPIV-positive samples.

Results A total of 35,538 samples were collected from the ARI cases, in which 1,397 were positive for HPIV(3.93%). No significant differences in annual and gender specific positive rates were observed (P>0.05). The positive rate varied significantly in different age groups (χ²=638.556, P<0.001), with the highest rate in age group 0–<6 years (7.14%). HPIV infection mainly occurred in summer, with the incidence peak in June 2024 and July 2025, respectively. Significant differences in positive rate were found among five areas (χ²=15.969, P=0.003) and among the samples from different sources, including those from inpatients, emergency and outpatient cases, outbreak-related cases, and others (χ²=64.798, P<0.001). The co-infection rate of HPIV (2.14%) was higher than the single infection rate (1.81%) (χ²=8.996, P=0.003), with co-infection with Haemophilus influenzae being the most common (12.81%). The proportion of co-infection in inpatients (54.55%) showed no significant difference from that in emergency and outpatient cases (54.17%) (χ²=0.014, P=0.904).

Conclusion HPIV was the main pathogen causing ARI in Henan during 2024–2025. Children aged ≤5 years were mainly affected. The incidence of HPIV infection peaked in summer. The co-infection rate was high, but it was not the main factor responsible for hospitalization.