Abstract
Respiratory tract infections are among the most common and important problems in clinical medicine. The approach to these infections begins with a basic understanding of the pathophysiology of the respiratory tract and how immune defences interact with pathogens. A number of distinct clinical syndromes can be defined which help physicians and clinical microbiologists develop a differential diagnosis of potential infecting pathogens. The type and severity of infection is often modulated by the medical characteristics of the patient, circumstances surrounding infection, geography and environmental exposures. Multiple laboratory test methodologies are available to aid clinical diagnosis and close communication between clinicians and laboratory personnel can optimise the efficiency and cost-effectiveness of diagnosis. Molecular testing for respiratory viruses has become widely used in the clinical setting and will expand to include other pathogens of the respiratory tract.