The duration of a viral fever depends on several factors including your age, health status, your immunity levels, and the type of viral infection. For instance, rhinoviruses cause the common cold and typically your fever would last for 1-2 days. Influenza viruses cause the flu and your fever would subside in 2-3 days.
Adenoviruses infects the airways and the intestinal tract and while it may take a week or more to recover completely, your fever would last for just 3-5 days.
The rotaviruses cause gastroenteritis which causes a mild to moderate fever that disappears within a day or two.
The coxsackie viruses cause hand -foot-and-mouth disease which begins with a low fever that lasts for 2-3 days.
While it is safe to say that most common viral fevers last for 1-5 days, there are more serious viral infections that can cause persistent high fever. If your fever is unusually high or if you are unable to bring it under control, you should consult your doctor to get a definite diagnosis.