Changes in Viral Dynamics Following the Legal Relaxation of COVID-19 Mitigation Measures in Japan From Children to Adults: A Single Center Study, 2020-2023

INTRODUCTION

Respiratory infections are an ongoing global health challenge. The COVID-19 pandemic triggered global nonpharmacological measures that reshaped public health. In Japan, the shift from legal to individual discretion in pandemic management started on May 8, 2023. However, it still unknown how the relaxation of measures affects respiratory pathogens across age groups.

METHODS

We collected 16,946 samples from 13,526 patients between February 2020 and September 2023, analyzing the circulating respiratory pathogen dynamics using FilmArray respiratory panel.

RESULTS

Our analysis revealed significant increases in the positivity rates of respiratory pathogens across multiple age groups after relaxation. The pathogens including adenovirus, Bordetella pertussis, parainfluenza 2 and parainfluenza 4 showed increased positivity predominantly in children aged under 10 years. Conversely, some pathogens including human metapneumovirus, rhinovirus/enterovirus, and respiratory virus (RSV) increased in broad range of age groups. SARS-CoV-2 positivity rates decreased in children under 10 years but increased in those aged over 60 years.

DISCUSSION

Age-stratified analysis reveals a dynamic pattern of circulating pathogen in each age group after relaxation measures. This study provides essential epidemiologic data that can guide strategies to protect different age groups and effectively respond to respiratory infections in post-COVID-19 era.

Influence of formalin fixation duration on RNA quality and quantity from formalin-fixed paraffin-embedded hepatocellular carcinoma tissues

Analyzing RNA samples from formalin-fixed paraffin-embedded (FFPE) tissues is essential for precision medicine. We investigated RNA quantity and quality from FFPE tumor tissues fixed in formalin for various times and compared sequencing metrics from next-generation sequencing (NGS). Hepatocellular carcinoma (HCC) tissues were fixed in 10% neutral buffered formalin (1-240 h) and FFPE blocks were prepared. Total RNA was extracted, and the quantity and quality were assessed using the NanoDrop, Qubit and Bioanalyzer. After preparing sequencing libraries, NGS was performed on the Oncomine Dx Multi-CDx system. Total RNA yields of all samples met the threshold required for NGS, but longer fixation times resulted in decreased total RNA and long RNA fragment (>200 nt) yields. NGS analysis showed fewer sequencing reads of internal control genes from RNA with longer fixation times. RNA extracted from FFPE blocks stored for 500 days had reduced RNA yield and quality compared with RNA obtained from FFPE blocks prepared immediately. In conclusion, short and over-fixation should be avoided because of their negative impact on sequencing quality. Fixation process should be finished promptly within recommended guidelines (6-72 h) for cancer patients.