Influenza, commonly known as the flu, is an acute and contagious viral infection caused by influenza A and B viruses, affecting the nose, throat, and sometimes the lungs. Typically seasonal, the flu is characterized by symptoms such as sudden onset of high fever, chills, muscle and body aches, severe fatigue, dry cough, sore throat, and nasal congestion. Hoarseness may also be observed in the later days of the illness. Most cases tend to resolve on their own with symptomatic treatment administered at home. However, medical evaluation and control may be necessary if symptoms worsen or signs of complications appear. One of the most effective methods of protection against the flu is the flu vaccine, which is recommended to be administered regularly.