Abstract
Respiratory tract infections are actually a spectrum of diseases associated with infection of both the upper and lower respiratory tract and include the common cold, otitis media, influenza-like illness, croup, bronchiolitis, and pneumonia. Viruses are the most common cause of respiratory tract infection and the viruses associated are more diverse than the respiratory diseases they cause with influenza viruses, respiratory syncytial virus, human metapneumovirus, parainfluenza viruses, adenovirus, rhinoviruses, enteroviruses, and human coronavirus having a major role. It is often difficult to clinically differentiate viral and bacterial etiologies for some respiratory diseases. Nucleic acid amplification assays provide a rapid and extremely sensitive means to detect respiratory viruses. Understanding the biology and pathogenesis of the associated viruses is key to understanding diagnostic testing limitations.