All of us have experienced the sore throat, runny nose, aching, and general sense of misery that announce the onset of the common cold. Other familiar signals include a cough, headache, and dry, sore, or sensitive breathing passages. The symptoms of both the common cold and the flu are often used somewhat interchangeably because both are caused by the same family of respiratory viruses. The distinction between the two depends on how severe the infection is and the range of symptoms. The flu, however, is usually more severe, develops quickly, and involves more of the body than a cold. A cold also occurs at any time of year while the flu, by contrast, usually develops in epidemics, normally in late fall and winter.
The flu produces a moderate to high fever, aching muscles, and acute fatigue. Vomiting and diarrhea may also develop and, in extreme cases, the flu may lead to pneumonia in particularly susceptible individuals. Other complications of the flu, although rare, include inflammation of the brain or heart, Reye’s syndrome, and croup. The end result depends upon the organism’s ability to resist by means of its army of defense systems.