Cough is due to a reflex, triggered by irritation of the upper airways, that causes a spasm of the chest and diaphragm muscles. It is the first defense of the lungs against infection. Ironically, it is also responsible for rapidly spreading infection. Treatment is based on the underlying cause.
Viral infections are the most common cause for acute cough in healthy children and adults. They are often accompanied with nasal congestion, a mild sore throat and fevers. The acute illness lasts five to seven day, but a dry irritating cough can continue for one or two more weeks. Treatment is symptomatic with cough and cold medications, unless secondary infections develop.
Viral infections can convert to secondary infections caused by bacteria. This pattern is classic for Influenza. The initial symptoms of fever, muscle aches, headaches and cough are due to the viral infection and last five to seven days. After starting to improve, a subset of patients relapse with secondary infections in the sinus and lungs that respond to antibiotics.
Acute bacterial infections can directly invade the throat (pharangitis), voice box (laryngitis), lung airways (bronchitis) or lung tissue (pneumonia). Symptoms include painful swallowing, hoarseness, wheezing and shortness of breath, respectively. Pneumococcus is aggressive bacteria and may evolve rapidly into a consolidated (dense) pneumonia or multi system failure called sepsis.
Any illness that irritates the lungs can potentially cause a cough. Other considerations include asthma or allergies, reflux or heartburn, and many heart conditions.
Cough associated with shortness of breath, blood in the sputum or sharp pain in the chest (pleurisy) requires an evaluation. A persistent cough over two weeks should also be evaluated.