Human parainfluenza viruses (HPIVs) are the leading causes of acute respiratory tract infections (ARTIs), particularly in children. During the COVID-19 pandemic, non-pharmaceutical interventions (NPIs) significantly influenced the epidemiology of respiratory viruses. This study analyzed 19,339 respiratory specimens from pediatric patients with ARTIs to detect HPIVs using PCR or tNGS, focusing on the period from 2021 to 2023. HPIVs were identified in 1395 patients (7.21%, 1395/19,339), with annual detection rates of 6.86% (303/4419) in 2021, 6.38% (331/5188) in 2022, and 7.82% (761/9732) in 2023. Notably, both the total number of tests and HPIV-positive cases increased in 2023 compared to 2021 and 2022. Seasonal analysis revealed a shift in HPIV prevalence from winter and spring in 2021–2022 to spring and summer in 2023. Most HPIV-positive cases were in children aged 0–7 years, with fewer infections among those aged 7–18 years. Since June 2022, HPIV-3 has been the most prevalent serotype (59.55%, 524/880), whereas HPIV-2 had the lowest proportion (0.80%, 7/880). The proportions of HPIV-1 (24.89%, 219/880) and HPIV-4 (15.45%, 136/880) were similar. Additionally, the incidence of co-infections with other common respiratory pathogens has increased since 2021. This study highlights rising HPIV detection rates post-COVID-19 and underscores the need for continuous surveillance of HPIVs to inform public health strategies for future epidemic seasons.

Background: During the COVID-19 pandemic, we continuously monitored the epidemiology of influenza virus among pediatric patients from January 2021 to December 2023 in Hainan Island, China. Methods: In this study, we collected 54,974 nasopharyngeal swab samples for influenza A Virus (IAV) testing and 53,151 samples for influenza B Virus (IBV) testing from pediatric outpatients. Additionally, we also collected 19,687 nasopharyngeal swab samples from pediatric inpatients for IAV and IBV testing. Outpatient samples were screened for influenza viruses (IVs) infection by the colloidal gold method. Targeted Next-Generation Sequencing (tNGS) was used to detect influenza virus infections in inpatients. Influenza virus types were identified by analyzing the HA/NA partial regions. Results: The findings revealed a significant decrease in the infection rate of IBV over the specified period, while the infection rate of IAV exhibited a rising trend. Additionally, B/Victoria lineage was the dominant epidemic strain in 2021, while the epidemic strains in 2022 and 2023 underwent a dynamic transformation from A/H3N2 to A/H1N1. Phylogenetic analysis revealed close relationships among the circulating strains. Nonetheless, because the sample size is limited, additional research is required. Conclusions: Our findings suggest that the predominant types of influenza viruses in the pediatric population are undergoing dynamic changes, influenced by the implementation and relaxation of non-pharmaceutical intervention measures. These findings highlight the need for adaptive influenza vaccination and containment strategies, particularly in tropical regions like Hainan, where climate and public health policies significantly impact viral transmission patterns. The insights gained from this study could inform more effective public health strategies in similar regions to mitigate the impact of influenza outbreaks in the future.

The absence of gestational age-specific reference intervals for serum N-acetyl-β-D-glucosaminidase (NAG) in pregnant women may lead to clinical misinterpretation. This study aimed to establish trimester-specific reference intervals for serum NAG in healthy pregnant women from Hainan, China, and to characterize its dynamic changes throughout gestation. In this cross-sectional study, 2416 healthy women with singleton pregnancies were stratified by gestational age into three groups: first trimester (1–12 +6 weeks; n = 1295), second trimester (13–27 +6 weeks; n = 670), and third trimester (28–40 weeks; n = 451). Serum NAG levels were measured, and trimester-specific reference intervals were established using the 2.5th to 97.5th percentiles. Serum NAG concentrations increased significantly with advancing gestation (P < 0.0001). The established reference intervals were 12.0–40.0 U/L for the first trimester, 16.0–63.2 U/L for the second trimester, and 29.3–107.0 U/L for the third trimester—all substantially higher than those of the non-pregnant control group (8.0–23.4 U/L). The median NAG level in the third trimester (56.2 U/L) represented a 143 % increase compared to the first trimester (22.5 U/L). This study provides the first gestational age-specific reference intervals for serum NAG in pregnant women in a tropical region of China. The findings confirm that physiological NAG levels increase progressively with gestational age. The use of non-pregnant reference intervals in clinical practice may lead to misclassification of renal function during pregnancy, underscoring the necessity of adopting trimester-specific reference standards in prenatal laboratory settings.