Investigating the incidence and clinical importance of secondary bacterial infections after viral respiratory infections

Abstract

Respiratory viruses are ubiquitous respiratory pathogens, readily infecting many people, in some cases causing severe diseases. These infections, however, are normally mild, and severe disease is mainly seen in those with underlying health conditions, such as chronic respiratory diseases (asthma, COPD) and immunosuppressive disorders. More recently, the identification of bacterial pathogens after a viral infection, either secondary to or during (co-infection) infection has been associated with more severe disease. Where bacterial co-infections seem to influence the severity of some viral respiratory tract infections. Several bacteria have been linked to increasing the severity of viral infection, but the most prevalent bacteria identified during secondary bacterial/co-infection is Streptococcus pneumoniae, which has been identified during diverse viral infections, including Respiratory Syncytial Virus (RSV), Influenza viruses, Adenovirus and Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, other bacteria have also been widely detected during severe viral respiratory infections, such as Staphylococcus aureus and Haemophilus influenzae. Identifying the most common bacterial pathogens associated with secondary bacterial/ co-infections during viral respiratory infection is crucial in terms of understanding the pathology of disease and planning for effective therapy. The increased severity of viral/ bacterial co-infections has been suggested to be due in part to altered antibacterial host immunity post-viral infection, resulting in increased cellular damage to the host cells during co- infection. So, damaged cells will provide good growth media for bacteria. Within this dissertation we summaries what is currently know about bacterial secondary/ co-infection post-viral respiratory infection, in regard to the incidence of this phenomenon, the clinical severity, and the mechanisms by which bacteria and viruses interact during co-infection. Understanding these mechanisms and discovering new mechanisms will help guide physicians on the best ways to treat co- infection and facilitate the discovery of novel alternative therapeutics.