Every year, from November to April, more than 60 million people in the United States are infected with an influenza virus, or the flu, according to KidsHealth, a health information site sponsored by the Nemours Foundation. The influenza virus is contagious, transmitted from one to another through droplets spread when someone coughs or sneezes. Flu symptoms usually start suddenly, according to the Centers for Disease Control and Prevention. Symptoms don't happen by accident--there are reasons for each miserable, uncomfortable sign that you have the flu.
Fever
A fever is part of the body's response to a viral infection, and influenza usually causes high body temperatures over 100 degrees. The body uses heat in an attempt to kill off invading viruses.
Body Aches
Body aches and fatigue are caused by early stages of dehydration caused by a rising fever. Dehydration may result in the loss of electrolytes, including potassium which is very important to muscle function. Lack of potassium leads to aching muscles, and an electrolyte imbalance makes a person feel exhausted.
Chills and Sweats
Chills and sweats are caused when the body temperature rises and falls rapidly. Chills accompany a rising temperature because the temperature of the room feels colder to the person with a fever. Sweats are the results of the body trying to cool itself quickly by sweating.
Stuffy Nose
Influenza is a virus that attacks mainly the respiratory system, affecting the nose, sinuses, throat and lungs. Much of the respiratory system has a protective lining that produces mucus to condition the air before it reaches the lungs. Viral infections can irritate the lining, causing the body to produce excess mucus as a protective measure. This excess mucus can build up in the sinuses, in the nose or even in the lungs.
Headache
Headaches are a common symptom of influenza. Headaches can be caused by sinus pressure, sinus infection caused by or accompanying the influenza virus or fever. Headache pain may be relieved by taking ibuprofen or other over-the-counter pain relievers.
Respiratory Distress
Influenza usually causes breathing problems and symptoms in the nose and throat because the influenza virus normally attacks the respiratory system. The flu is not a digestive disorder and so it rarely causes an upset stomach, according to MedlinePlus, a publication of the National Institutes of Health.
Coughing and Sneezing
Coughing and sneezing are the body's way of getting rid of excess mucus and foreign debris. Coughing and sneezing are the virus's way of spreading to a new host. Viruses pass through the air and enter the next person's nose or mouth. Coughing or sneezing into the inside of the elbow can help prevent the spread of the virus, and frequent hand washing can reduce transmitting or catching the virus.
