Respiratory tract infectious Diseases
Respiratory tract infections are actually a spectrum of diseases associated with infection of both the upper and lower respiratory tract. 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.
Upper respiratory tract infections are certain types of influenza, and the common cold. Symptoms of URIs can include cough, sore throat, runny nose, nasal congestion, headache, low grade fever, facial pressure and sneezing.
Lower respiratory tract infections are generally more serious than upper respiratory infections. LRIs are the leading cause of death among all infectious diseases. The two most common LRIs are bronchitis and pneumonia. Influenza affects both the upper and lower respiratory tracts, but more dangerous strains such as the highly pernicious H5N1 tend to bind to receptors deep in the lungs.