Common maladies are illnesses that are widespread and affect many people. One of the most common maladies is the cold, which is caused by a virus and is characterized by symptoms such as a runny nose, sore throat, and coughing. Other common maladies include the flu, which is also caused by a virus and is characterized by fever, body aches, and fatigue; and allergies, which are caused by an overreaction of the immune system to certain substances.