Influenza (the flu) is a respiratory infection afflicting between 5 and 20 percent of people in the United States each year, according to MedlinePlus. For some, the flu can be dangerous, leading to hospitalization and even death. The flu is often mistaken for the common cold. Knowing which signs indicate the flu, however, can help you pursue prompt treatment, offering a better outcome and lessening the duration of the illness.
Headache/Sore Throat
One of the first indications of the flu may be a headache. To determine whether you are experiencing a typical headache or initial flu symptoms, consider other symptoms that may be present. If you also have a sore throat or cough, you may not have a simple cold. According to MedlinePlus, headaches are rarely caused by the common cold.
Chills/Body Aches
Chills and body aches are another initial sign of the flu, causing you to feel sudden cold sensations as well as dull pain throughout your body. Chills are often a sign of infection, caused by rapid muscle contraction and relaxation, according to MedlinePlus. They are the body's attempt to create heat when it feels cold and often precede a fever.
Fever
A fever occurs when the body attempts to ward off infection, causing the temperature to rise. While body temperatures vary slightly form person to person, when an adult's temperature rises above 101 degrees F, it may be a sign of the flu, according to the Mayo Clinic.
Loss of Appetite/Nausea
A loss of appetite may occur. If food suddenly becomes unappealing, you may be experiencing the first symptoms of the flu. You may also feel nauseous or sick to your stomach.
Children's Initial Flu Symptoms
A child may exhibit different initial symptoms of the flu than adults, such as stomach pain, vomiting and diarrhea. All of these symptoms occur suddenly and can indicate the flu.
