Based on our preexisting knowledge of viral infections, infected individuals are only contagious when they have a fever; this typically lasts about two to 14 days. This duration is dependent upon a number of factors, such as overall health, if any preexisting conditions are present (such as heart disease or diabetes), diet, level of physical activity, and immune health. Some individuals may experience a fever that lasts only a day, while others may run a feverous temperature for over a week. This is typically accompanied by symptoms such as body aches, lack of appetite, lethargy (fatigue), sore throat, and headache.