Flu which is also called "Influenza", is a very contagious viral infection of the upper respiratory tract. Because the illness can be spread easily by coughing and sneezing, influenza epidemics are very common, especially in the winter season. There are over 200 different viruses can cause colds and flu, and strains of these viruses are constantly changing, so vaccinations against influenza have been only partly successful in preventing outbreaks of the disease. The symptoms of influenza begin much like those of the common cold: body aches, fatigue, fever, and headache. Many times the person you will feel hot  then and cold and shaking. Most flu sufferers have a dry throat and cough. Nausea and vomiting may occur as well. The person with the influenza or flu is so weak and uncomfortable that they do not feel like eating or doing anything. Influenza is rarely dangerous in healthy adults 60 years of age or younger, but it does make a person more susceptible to pneumonia, ear infections, and sinus trouble. In people 65 or older, serious respiratory infections such as pneumonia and influenza are the 5th leading cause of death, so the flu is a very serious infection for older people.