The influenza virus causes the illness commonly known as the flu. This is a highly contagious respiratory illness that passes from person to person through contact with the virus that enters the body through the nose, mouth or eyes. Only one or two symptoms does not indicate the flu. Instead, the flu is a combination of several of symptoms, the most important being sudden onset with high fevers.
Respiratory
According to the Centers for Disease Control and Prevention (CDC), a stuffy nose, sneezing or sore throat may sometimes occur with the flu, but chest discomfort or coughing is frequently an issue. The most significant complications from the flu are also respiratory in nature, such as pneumonia or bronchitis. These complications can become life threatening, especially in the elderly, young children and those who suffer from immune compromising illnesses such as asthma or cancer.
Fever
According to the U.S. Department of Health and Human Services, the flu is characterized by a high fever, often between 102 and 104 degrees Fahrenheit. The fever will last between three and four days and may or may not ease with anti-fever medications, such as aspirin or acetaminophen. The anti-fever medications will work more effectively as the viral infection begins to diminish. According to the CDC, symptoms of the flu will come on suddenly and without warning. This is different from cold symptoms. A cold will often manifest itself over several days, starting with a headache or stuffy nose.
Headache
Fever with the flu will be accompanied by a prominent and significant headache that resolves slowly as the fever lessens. According to the U.S. Department of Health and Human Services, a headache with the common cold is rare. This differentiation between a cold and the flu helps the doctor determine the correct course of treatment.
Body Aches
The CDC advises that body aches and extreme tiredness are signs of an influenza viral infection. They also warn that these symptoms alone do not indicate the flu. There are many other illnesses or conditions that can cause body aches or extreme tiredness, including the common cold.
