Introduction

Respiratory viruses in general produce relatively trivial disease, localised to the upper respiratory tract resulting in such syndromes as the common cold, pharyngitis/sore throat, tracheitis and otitis media. Viral pneumonia or other lower respiratory tract infections are relatively uncommon, but when they do occur are often severe, sometimes fulminant and not infrequently fatal. Unlike the situation with bacterial infections the antimicrobial drug armamentarium is limited in numbers and effectiveness. This chapter will focus on lower respiratory infections in adults. Paediatric lower respiratory tract infections are covered in Chapter 23 and further aspects in the immunocompromised host setting in Chapter 21. Cytomegalovirus because of its special relationship to the compromised host is covered in Chapter 10.

Only a few pathogenic viruses have a potential for invasion of the lower respiratory tract (Table 9.1). Among these the Orthomyxoviridae (notably influenza) are the most prominent in terms of numbers of young and elderly people infected, disabled or dying. A pandemic of influenza A is predicted for the near future. Among the Paramyxoviridae, respiratory syncytial virus is of importance for the severity of the illness it can produce, its possible underestimated role in the elderly and modern assessment of ribavirin therapy. The remaining viruses include parainfluenza (Paramyxoviridae), herpes simplex and Epstein–Barr virus (DNA Herpesviridae), and Adenoviridae. In addition, there are a few other viruses which invade the respiratory tract as part of a more generalised viraemic syndrome, such as measles and varicella.