Infectious respiratory pathogens among patients with acute exacerbation of idiopathic pulmonary fibrosis during the coronavirus disease 2019 pandemic in Japan

Background: Few studies have investigated the prevalence of pathogens in patients with acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF), specifically, the interactions between respiratory pathogens and AE-IPF during the coronavirus disease 2019 (COVID-19) pandemic. Objectives: We aimed to analyze pathogens in patients with AE-IPF between September 2020 and December 2022. Methods: This retrospective observational study was conducted at our hospital between September 2020 and December 2022. In patients with AE-IPF, pre -hospitalization polymerase chain reaction (PCR) tests for respiratory pathogens, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), were performed using multiplex PCR or Smart Gene assay with nasopharyngeal swab specimens. Microbiological assays, including Gram staining, sputum cultures, blood cultures, and urinary antigen tests for Streptococcus pneumoniae and Legionella pneumophila , were also performed. Results: Forty-nine patients with AE-IPF were included. The median age was 75 years old and 42 (86 %) were male. Only one of the 49 patients (2 %) was positive for SARS-CoV-2. Two of 28 patients (7 %) were positive for human rhinovirus/enterovirus. No bacteria were detected in sputum culture, blood culture, or urinary antigen tests. Conclusions: The detection frequency of SARS-CoV-2 infection in patients with AE-IPF was lower than that of human rhinovirus/enterovirus. Continuous analysis for the presence of pathogens is necessary for appropriate infection control because respiratory viruses may increase as the coronavirus pandemic subsides.