Influenza (“flu”) is a common virus that causes respiratory infections. Generally, this infection is associated with a short illness with respiratory symptoms (cough, sore throat, runny nose) with systemic symptoms (fevers, chills, muscle aches and sudden fatigue). This illness is usually more significant than the common cold, but can be similar to illnesses caused by other viruses.
In some patients, particularly those with chronic illnesses and the elderly, influenza can be severe and require hospitalisation. Influenza can cause illness directly by infection of the lungs (pneumonitis), by predisposing to secondary bacterial infection (pneumonia), or by de-stabilizing underlying medical conditions.
In Australia, influenza immunisation is available free of charge to patients at high risk of complications (particularly the elderly, those with co-morbidities, Indigenous Australians and pregnant women). The influenza vaccine provides moderate protection against influenza infection and its complications. New "enhanced" vaccines were introduced for the elderly in 2018. Antiviral treatment is also available on prescription from medical practitioners.