Influenza, commonly known as the flu, is a highly contagious viral infection that affects the respiratory system. It is caused by influenza viruses that infect the nose, throat, and sometimes the lungs. The flu can cause mild to severe illness and, in some cases, can lead to hospitalization or death.

The flu is different from a common cold and typically comes on suddenly. It is crucial to differentiate between the 2 in order to seek appropriate medical treatment promptly. Unlike the common cold, the flu can lead to serious complications, particularly in vulnerable populations such as young children, elderly adults, and people with certain chronic health conditions. Influenza is also different from the viruses that cause stomach bugs, which are commonly referred to as the “flu.”