Respiratory Diseases, Acute

a group of infectious diseases, mainly viral in origin, characterized by inflammation of the upper respiratory tract. The source of infection is an infected person or a carrier of the virus. The causative agent is spread together with particles of mucus and saliva during coughing, sneezing, or conversation; infection may also spread by means of linens, towels, or dishes. Such environmental factors as cold, dust, and chemicals play an important role in the inception of some acute respiratory diseases.

The acute respiratory diseases include influenza, parainfluenza, and adenoviral, reoviral, rhinoviral, and enteroviral diseases, as well as some infections caused by mycoplasmas, streptococci, and staphylococci. Immunity after a disease caused by one agent does not give protection against another agent, and therefore a person may have acute respiratory diseases several times a year. With the exception of influenza, the diseases are characterized by moderate fever and by manifestations of rhinitis, pharyngitis, laryngitis, tracheitis, and bronchitis, sometimes combined with inflammation of the connective membrane of the eyes (conjunctivitis).

In the absence of complications, acute respiratory diseases usually last five to eight days. Specific preventive measures have been developed only against influenza; the nonspecific preventive measures are identical for all acute respiratory diseases, including influenza. Prevention against chilling and maintenance of an optimal microclimate at places of work are important preventive measures.