Respiratory infections include the infectious diseases of the respiratory tract. Such infections can be classified as lower respiratory tract infection or upper respiratory tract infection. The lower respiratory tract infections are more serious than the upper respiratory tract infections. Some respiratory tract infections are sinusitis, tonsillitis, pharyngitis, influenza, bronchitis and pneumonia. Human orthopneumovirus is a major cause of lower respiratory tract infections. It generally causes conditions like bronchiolitis and pneumonia. These can be diagnosed through physical examination, skin monitoring to check for hypoxemia, chest X-rays, blood tests, and lab test of respiratory secretions. This book explores all the important aspects of respiratory infections in the present day scenario. It includes some of the vital pieces of work being conducted across the world, on various topics related to the diagnosis and treatment of respiratory infections. This book is a resource guide for doctors as well as students.