Epidemiology of lower respiratory tract infections in adults

Introduction: Lower respiratory tract infections (LRTIs) are the leading infectious disease cause of death in the world and the fifth overall cause of death. From an epidemiological point of view, most consider pneumonia, influenza, bronchitis (including acute exacerbations in chronic obstructive pulmonary disease [AECOPD]), and bronchiolitis to be the most important LRTIs. Areas covered: This review will describe the epidemiology of LRTIs in adults focusing on community-acquired pneumonia, influenza, and AECOPD, utilizing data from the more recent literature. Expert commentary: LRTIs remain exceedingly common, although there have been significant changes in their epidemiology over recent years, both with regard to their frequency and the infecting pathogens. Part of the change in the epidemiology may relate to changing population demographics, the varying prevalence of smoking, and the introduction of the pneumococcal conjugate vaccine in children and patterns of vaccine usage. Furthermore, antigenic variations in the influenza viruses dictate the frequency and characteristics of the influenza epidemics and pandemics.