Flu can cause a variety of symptoms. They can be mild or severe. Symptoms and severity depend on the type of virus, your age and overall health.
Although it is a respiratory virus, flu can affect other body systems. This makes you feel sick all over. Symptoms can include any or all of the following:
Moderate to high fever (101 to 103 degrees Fahrenheit)
Dangerous complications also can develop from flu. One of the most feared complications is a bacterial superinfection. A superinfection occurs when the influenza virus attacks a lung and weakens its defenses. This makes the body susceptible to bacterial pneumonia.
Certain people are especially vulnerable to complications. These include:
People older than 50
People with certain chronic diseases
People with suppressed immune systems