Changes in epidemiology of respiratory diseases and infections during the coronavirus disease 2019 pandemic

Abstract

The coronavirus disease 2019 (COVID-19) pandemic has changed mankind significantly in terms of the mortality and morbidity caused by the viral infection, as well as changes in human behaviour due to social distancing. During the pandemic, Hong Kong was one of the first cities worldwide to implement universal masking and social distancing measures. This thesis presents a series of studies carried out to investigate the possible effects of changes in human behaviour on the epidemiology of respiratory diseases and infections in Hong Kong during the COVID-19 pandemic. The first two chapters of the thesis focus on the effect of universal masking and social distancing on hospitalisations due to acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and asthma. The first chapter focuses on the changes in a university-affiliated hospital for AECOPD, while the second chapter investigates territory-wide hospitalisations due to asthma exacerbation. Other environmental factors, such as air quality and ambient temperature changes, are also accounted for. These studies showed a decrease in hospitalisations due to AECOPD and asthma exacerbation that was associated with an increased masking percentage in Hong Kong. Based on these results, the 2022 Global Initiative for Chronic Obstructive Lung Disease (GOLD) report, an international guideline for COPD, recommended that COPD patients wear masks to decrease the risk of AECOPD. The next two chapters focus on changes in the epidemiology of infections during the COVID-19 pandemic. Studies were performed on two important global infectious diseases, namely invasive pneumococcal disease (IPD) and tuberculosis (TB), both of which are notifiable diseases in Hong Kong. In addition to IPD, our study included pneumococcal pneumonia and all-cause pneumonia. The findings showed that universal masking was associated with a decrease in the incidence of both IPD and pneumococcal pneumonia and all-cause pneumonia during the COVID-19 period, with a greater reduction compared to pneumococcal conjugate vaccine. This highlights the importance of masking in IPD prevention. The study on TB describes the epidemiology of TB in the baseline period from 2015 to 2019 and COVID-19 period from 2020 to 2022 and reveals a higher mortality rate for TB co-infection with influenza or COVID-19, which is a novel finding of this study. We recommend vaccination for both influenza and COVID-19 for subjects with a high risk of TB infection or reactivation. The last study evaluated changes in the epidemiology of culture-positive pleural empyema during the COVID-19 pandemic. Pleural empyema is a disease that incurs high hospital costs, with a significant mortality and morbidity burden. Our study showed higher levels of polymicrobial organisms during the COVID-19 period, which can aid clinicians in managing patients with pleural empyema. This series of studies illustrates, from a clinical perspective, the changes in the epidemiology of respiratory diseases and infections during the COVID-19 pandemic, with novel findings that can guide clinicians in managing them.