# The course of respiratory tract infections in pediatric hemato-oncology patients during and after the COVID-19 pandemic: single center retrospective cohort study

## TL;DR

This study examines respiratory tract infections in children with blood or cancer disorders before and after the COVID-19 pandemic, finding increased infection rates after pandemic restrictions eased.

## Contribution

The study identifies rhinovirus/enterovirus as the most common cause of RTI in this vulnerable group and highlights a post-pandemic surge in infections.

## Key findings

- Rhinovirus/enterovirus and influenza A/B were the most common RTI pathogens.
- Post-pandemic RTI outbreaks increased significantly after non-pharmacological measures were reduced.
- LRTI was associated with more severe clinical outcomes compared to URTI.

## Abstract

Respiratory tract infections (RTI) are a leading cause of hospitalization in children and remain a significant contributor to morbidity. Our study aimed to examine the epidemiology of RTI in children with hemato-oncologic disease during and after the coronavirus 2019 (COVID-19) pandemic.

This retrospective study evaluated nasopharyngeal swab samples that were tested using multiplex PCR from 185 children hospitalized with respiratory symptoms between January 2020 and March 2025.

A total of 313 RTI agents were identified in 185 children with hemato-oncologic disorders across 271 infectious episodes. The median age was 6 years. The infection rates for upper respiratory tract infections (URTI) and lower respiratory tract infections (LRTI) were 45% and 55%, respectively. A statistically significant difference was found between patients with URTI and LRTI in terms of CRP, tachypnea, dyspnea, duration of fever, duration of hospital stay due to infection, need for intensive care unit, and oxygen requirements (p < 0.05). The most common pathogens causing RTI were rhinovirus/enterovirus and influenza A/B, and their frequencies increased significantly in the post-pandemic period. Co-infections were significantly more common in the LRTI group during the post-pandemic period. Nine out of 185 children (5%) died.

Children with hematologic-oncologic disease are at risk for RTI. The most common agent was found to be rhinovirus/enterovirus. RTI outbreaks were observed especially as a result of the reductions in non-pharmacological measures implemented during the pandemic. In our study, the largest RTI outbreak was seen between November 2023 and May 2024 following the end of the COVID-19 pandemic.