The flu affects many major organs of the body. The kidneys included, that is one reason for the drinking of extra fluid. Your Kidneys are located in you lower back. Another reason is if you have lain down for a long time, this tends to stiffen those muscles. If this answer helped, please help me by clicking on a star next to the RATE THIS ANSWER, IT will make sure my answer gets counted, thanks and have a Blessed day..*p
