# Comparison of respiratory pathogen infections in hospitalized patients before and during the COVID-19 pandemic in Shanghai, China

## TL;DR

This study compares respiratory infections in hospitalized patients in Shanghai before and during the COVID-19 pandemic, finding a significant drop in most pathogens but an increase in Legionella pneumophila.

## Contribution

The study reveals how the pandemic altered the prevalence of respiratory pathogens and highlights shifts in infection patterns over time.

## Key findings

- Respiratory pathogen detection rates dropped from 32.05% pre-pandemic to 11.48% during the pandemic.
- Mycoplasma pneumoniae, FluB, and PIV infections decreased significantly, while Legionella pneumophila increased.
- Children had the highest infection rates compared to other age groups.

## Abstract

This study aimed to assess the impact of COVID-19 on the prevalence of
respiratory pathogens among hospitalized patients with respiratory tract
infections in Shanghai, China. Patients with acute respiratory infections
(ARIs) hospitalized at Putuo Hospital, Shanghai University of Traditional
Chinese Medicine from January 2017 to December 2022 were collected. Indirect
immunofluorescence assay (IFA) was used to detect the IgM antibody of nine
common pathogens, including Chlamydia pneumoniae (CP),
Mycoplasma pneumoniae (MP), parainfluenza virus (PIV),
respiratory syncytial virus (RSV), influenza virus A (FluA), influenza virus
B (FluB), adenovirus (ADV), Legionella pneumophila (Lp),
and Coxiella burnetii (Cb). A total of 24,933 eligible
patients were enrolled. The overall detection rate of respiratory pathogens
in the pre-outbreak group (2017–2019, 32.05%) was significantly
higher than that in the outbreak group (2020–2022, 11.48%,
P < 0.001). MP (16.03%), Lp (2.43%), FluB
(1.73%), and PIV (1.64%) were the main pathogens. Positivity for MP, FluB,
and PIV declined significantly, whereas the detection rate of Lp was
increased (P < 0.05) during the 2020–2022
period compared with the 2017–2019 period. Children (73.21%)
experienced a significantly higher infection rate than adolescents (65.35%),
adults (25.20%), and older adults (15.40%). MP+PIV was the most common
co-detection pattern. The detection of CP, MP, PIV, RSV, FluB, ADV, and Lp
differed significantly between the two periods. From 2020 to 2022, the
detection rates of CP, MP, PIV, RSV, FluB, and ADV decreased, whereas the
detection of Lp increased. Knowledge of common pathogens’ dynamics
could serve as a reference for further prevention and control of ARIs.

This study leverages the changes in the common respiratory spectrum
pre-pandemic and during the COVID-19 pandemic in hospitalized patients in
Shanghai. These data may serve as a scientific foundation for the prevention
and management of ARIs. Doctors and policymakers should pay attention to the
changes in the epidemic trends and types of respiratory pathogens and
maintain monitoring of respiratory pathogens to better control the
prevalence of respiratory pathogens.