Definition and EtiologyTop
Influenza complicated by pneumonia rarely develops in otherwise healthy individuals. The risk is increased by chronic lung diseases (mainly chronic obstructive pulmonary disease), valvular heart disease, diabetes mellitus, nephrotic syndrome, immunosuppressive treatment, advanced age, and pregnancy. The same groups of patients are at high risk of infection with Streptococcus pneumoniae, which is a cause of pneumonia following initial infection with influenza.
Diagnosis is based on clinical features (manifestations of pneumonia with concomitant rhinitis and myalgia) and onset during an influenza season. Chest radiographs reveal bilateral, symmetric, diffuse opacities. The diagnosis may be confirmed by isolating the virus from sputum, bronchial secretions, or a pharyngeal swab, or by immunologic studies. In the current epidemiologic environment (as of October 2021), viral pneumonias are overwhelmingly due to coronavirus disease 2019 (COVID-19).
Symptomatic treatment and antiviral drugs (see Influenza).