disease

Influenza

An acute respiratory disease caused by the influenza virus. Affects the respiratory tract. Considered the most severe among acute respiratory viral infections. The disease manifests suddenly with muscle weakness, fever, cough, sore throat, severe headache, and photophobia. Upper respiratory tract involvement starts with cough, chest pain, and runny nose. Later, throat pain, shortness of breath, and hoarseness appear. Rare strains of influenza can have gastrointestinal symptoms. Mortality from influenza increases in crowded conditions or during the epidemics.